Widen feed ids to 32 opaque bytes and fix decimals at 18

[Fletch153]

Summary

• Feed ids become 32 opaque bytes; nothing is derived from them anymore.
• Every answer is stored and served at a fixed 18 decimals across cache and proxy.

Context

A feed id used to carry meaning: byte 7 encoded the feed's decimals, and 32-byte report ids were truncated to their high 16 bytes before matching. That coupled integrators to an id encoding scheme and let two distinct wire ids collide after truncation. Ids are now random bytes as far as the contracts are concerned, and the answer format is a protocol constant instead of a per-feed property. Reduced-precision serving, if ever needed, will be a proxy layered on top rather than state in these contracts.

Changes

• Cache: ids widen to BytesN<32> and a report must match the configured id exactly, truncation is gone. decimals() serves a constant 18 for configured feeds; the derivation from id bytes is removed.
• Proxy: same surface as before (latest_round, get_round, decimals, description) on the wider id type. decimals() still reads through to the cache, so a future cache change propagates without touching the proxy.
• Tests: byte7 derivation coverage replaced with fixed-decimals coverage, and the truncation test now asserts exact id matching. Both self-upgrade wasm fixtures are rebuilt for the new ABI.

Testing

• Full contract suite passes: 190 cache, 31 proxy, 9 common.

Notes

• Stacked on the batched-reads branch (PR Make latest_round accept one or many data ids #182).

[github-actions]

Soroban Contract Test Coverage

92.64% line coverage — 18001 / 19431 lines hit

Metric	Hit	Total	Coverage
Lines	18001	19431	92.64%
Functions	1189	1529	77.76%
Regions	33476	35839	93.41%

Per-Contract Breakdown

Contract	Lines (Hit / Total)	Line Cov	Funcs (Hit / Total)	Func Cov
other	18001 / 19431	92.6%	1189 / 1529	77.8%

Full file-level coverage report

Filename                                                 Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ccip-ramp-registry/src/lib.rs                                188                75    60.11%           8                 3    62.50%         104                41    60.58%           0                 0         -
ccip-ramp-registry/src/test.rs                               214                 0   100.00%           5                 0   100.00%         128                 0   100.00%           0                 0         -
ccip-ramp-registry/src/types.rs                               83                11    86.75%          17                 6    64.71%          83                11    86.75%           0                 0         -
ccvs/committee-verifier/src/lib.rs                           588                54    90.82%          26                 2    92.31%         382                10    97.38%           0                 0         -
ccvs/committee-verifier/src/test.rs                         1300                25    98.08%          48                 2    95.83%         587                13    97.79%           0                 0         -
ccvs/committee-verifier/src/types.rs                          17                 8    52.94%           6                 5    16.67%          14                 7    50.00%           0                 0         -
ccvs/versioned-verifier-resolver/src/lib.rs                  287                21    92.68%          14                 1    92.86%         162                 4    97.53%           0                 0         -
ccvs/versioned-verifier-resolver/src/test.rs                 680                 9    98.68%          20                 0   100.00%         359                 3    99.16%           0                 0         -
ccvs/versioned-verifier-resolver/src/types.rs                 89                 6    93.26%          16                 4    75.00%          83                 4    95.18%           0                 0         -
common/authorization/src/allowlist.rs                        167                51    69.46%          12                 4    66.67%         110                40    63.64%           0                 0         -
common/authorization/src/lib.rs                              426                27    93.66%          16                 0   100.00%         277                16    94.22%           0                 0         -
common/authorization/src/ownable.rs                          102                13    87.25%           9                 1    88.89%          62                 6    90.32%           0                 0         -
common/authorization/src/test.rs                            1195                 0   100.00%          57                 0   100.00%         462                 0   100.00%           0                 0         -
common/guard/src/initializable.rs                             30                 1    96.67%           4                 0   100.00%          22                 1    95.45%           0                 0         -
common/guard/src/lib.rs                                       32                 1    96.88%           4                 0   100.00%          22                 0   100.00%           0                 0         -
common/guard/src/test.rs                                     101                 0   100.00%           8                 0   100.00%          47                 0   100.00%           0                 0         -
common/helpers/src/curse_checkable.rs                        103                24    76.70%           6                 1    83.33%          56                12    78.57%           0                 0         -
common/helpers/src/map_updater.rs                             94                15    84.04%           7                 3    57.14%          39                 8    79.49%           0                 0         -
common/helpers/src/soroban_invoke.rs                         204                 4    98.04%           8                 0   100.00%          81                 0   100.00%           0                 0         -
common/interfaces/src/ccip_receiver.rs                         8                 8     0.00%           8                 8     0.00%           8                 8     0.00%           0                 0         -
common/interfaces/src/committee_verifier.rs                   13                13     0.00%          13                13     0.00%          13                13     0.00%           0                 0         -
common/interfaces/src/fee_quoter.rs                           17                17     0.00%          17                17     0.00%          17                17     0.00%           0                 0         -
common/interfaces/src/offramp.rs                              11                11     0.00%          11                11     0.00%          11                11     0.00%           0                 0         -
common/interfaces/src/onramp.rs                                9                 9     0.00%           9                 9     0.00%           9                 9     0.00%           0                 0         -
common/interfaces/src/ramp_registry.rs                         5                 5     0.00%           5                 5     0.00%           5                 5     0.00%           0                 0         -
common/interfaces/src/rmn_proxy.rs                             6                 6     0.00%           6                 6     0.00%           6                 6     0.00%           0                 0         -
common/interfaces/src/router.rs                                9                 9     0.00%           9                 9     0.00%           9                 9     0.00%           0                 0         -
common/interfaces/src/siloed_lock_release_pool.rs             21                21     0.00%          21                21     0.00%          21                21     0.00%           0                 0         -
common/interfaces/src/token_admin_registry.rs                  8                 8     0.00%           8                 8     0.00%           8                 8     0.00%           0                 0         -
common/interfaces/src/token_lock_box.rs                        6                 6     0.00%           6                 6     0.00%           6                 6     0.00%           0                 0         -
common/interfaces/src/token_pool.rs                           11                11     0.00%          11                11     0.00%          11                11     0.00%           0                 0         -
common/interfaces/src/versioned_verifier_resolver.rs          10                10     0.00%          10                10     0.00%          10                10     0.00%           0                 0         -
common/message/src/lib.rs                                    586                41    93.00%          28                 4    85.71%         298                 9    96.98%           0                 0         -
common/message/src/test.rs                                   641                 2    99.69%          28                 0   100.00%         323                 0   100.00%           0                 0         -
common/pool/src/decimals.rs                                  109                10    90.83%           6                 0   100.00%          76                 3    96.05%           0                 0         -
common/pool/src/finality_codec.rs                             52                 1    98.08%           3                 0   100.00%          41                 0   100.00%           0                 0         -
common/pool/src/lib.rs                                       460                31    93.26%          32                 1    96.88%         409                26    93.64%           0                 0         -
common/pool/src/rate_limit.rs                                180                 7    96.11%           9                 0   100.00%         145                 3    97.93%           0                 0         -
common/pool/src/types.rs                                      20                14    30.00%          16                14    12.50%          30                14    53.33%           0                 0         -
common/signature/src/config.rs                                44                12    72.73%           6                 2    66.67%          28                 5    82.14%           0                 0         -
common/signature/src/quorum.rs                                68                 1    98.53%           2                 0   100.00%          44                 1    97.73%           0                 0         -
common/signature/src/scheme.rs                                45                 0   100.00%           2                 0   100.00%          29                 0   100.00%           0                 0         -
cre/forwarder/src/error.rs                                     8                 3    62.50%           1                 0   100.00%           8                 3    62.50%           0                 0         -
cre/forwarder/src/lib.rs                                     460                24    94.78%          18                 0   100.00%         313                 7    97.76%           0                 0         -
cre/forwarder/src/test.rs                                   2840                14    99.51%         125                 2    98.40%        1176                 8    99.32%           0                 0         -
cre/forwarder/src/types.rs                                    62                 6    90.32%          10                 6    40.00%          36                 6    83.33%           0                 0         -
cre/test/read_fixture/src/lib.rs                             125               125     0.00%          33                33     0.00%         103               103     0.00%           0                 0         -
cre/test/receiver/src/lib.rs                                  30                30     0.00%           4                 4     0.00%          15                15     0.00%           0                 0         -
fee-quoter/src/lib.rs                                        771               164    78.73%          20                 3    85.00%         527               100    81.02%           0                 0         -
fee-quoter/src/test.rs                                       861                 0   100.00%          17                 0   100.00%         427                 0   100.00%           0                 0         -
fee-quoter/src/types.rs                                       13                13     0.00%          13                13     0.00%          13                13     0.00%           0                 0         -
mcms/src/abi_encoding.rs                                     216                 4    98.15%          10                 0   100.00%          98                 1    98.98%           0                 0         -
mcms/src/constants.rs                                         10                 0   100.00%           2                 0   100.00%           6                 0   100.00%           0                 0         -
mcms/src/crypto.rs                                           202                 3    98.51%           7                 0   100.00%         109                 2    98.17%           0                 0         -
mcms/src/error.rs                                              8                 4    50.00%           1                 0   100.00%           8                 4    50.00%           0                 0         -
mcms/src/lib.rs                                              713                50    92.99%          20                 0   100.00%         483                23    95.24%           0                 0         -
mcms/src/test.rs                                            2278                19    99.17%          59                 0   100.00%        1095                 2    99.82%           0                 0         -
mcms/src/types.rs                                             10                10     0.00%          10                10     0.00%          10                10     0.00%           0                 0         -
offramp/src/lib.rs                                           729               400    45.13%          23                 8    65.22%         473               224    52.64%           0                 0         -
offramp/src/test.rs                                          890                 0   100.00%          28                 0   100.00%         363                 0   100.00%           0                 0         -
offramp/src/types.rs                                          21                 9    57.14%           6                 5    16.67%          17                 7    58.82%           0                 0         -
onramp/src/lib.rs                                           1181               149    87.38%          27                 2    92.59%         739                61    91.75%           0                 0         -
onramp/src/test.rs                                          1591                 4    99.75%          37                 0   100.00%         708                 4    99.44%           0                 0         -
onramp/src/types.rs                                           23                 9    60.87%           6                 5    16.67%          19                 7    63.16%           0                 0         -
pools/burn-mint-pool/src/lib.rs                              390               107    72.56%          28                 9    67.86%         282                55    80.50%           0                 0         -
pools/burn-mint-pool/src/test.rs                            2671                24    99.10%          56                 5    91.07%        1744                55    96.85%           0                 0         -
pools/lock-release-pool/src/lib.rs                           404               100    75.25%          28                 8    71.43%         288                48    83.33%           0                 0         -
pools/lock-release-pool/src/test.rs                         2330                24    98.97%          55                 5    90.91%        1524                55    96.39%           0                 0         -
pools/siloed-lock-release-pool/src/lib.rs                    556               196    64.75%          38                17    55.26%         384               123    67.97%           0                 0         -
pools/siloed-lock-release-pool/src/test.rs                  1303                12    99.08%          38                 2    94.74%         695                18    97.41%           0                 0         -
pools/token-lock-box/src/lib.rs                              197                17    91.37%          13                 1    92.31%         113                 2    98.23%           0                 0         -
pools/token-lock-box/src/test.rs                             257                 0   100.00%           7                 0   100.00%          73                 0   100.00%           0                 0         -
registry/src/lib.rs                                            8                 0   100.00%           1                 0   100.00%           3                 0   100.00%           0                 0         -
registry/src/test.rs                                          27                 0   100.00%           1                 0   100.00%          11                 0   100.00%           0                 0         -
rmn_proxy/src/lib.rs                                          66                12    81.82%           5                 1    80.00%          34                 3    91.18%           0                 0         -
rmn_proxy/src/test.rs                                        279                 0   100.00%          11                 0   100.00%          91                 0   100.00%           0                 0         -
rmn_remote/src/lib.rs                                        302                26    91.39%          16                 1    93.75%         171                10    94.15%           0                 0         -
rmn_remote/src/test.rs                                       393                 0   100.00%          14                 0   100.00%         133                 0   100.00%           0                 0         -
router/src/lib.rs                                            593                87    85.33%          18                 1    94.44%         374                43    88.50%           0                 0         -
router/src/test.rs                                          1186                 0   100.00%          29                 0   100.00%         497                 0   100.00%           0                 0         -
router/src/test_panic_receiver.rs                              5                 0   100.00%           2                 0   100.00%           5                 0   100.00%           0                 0         -
router/src/types.rs                                            3                 3     0.00%           3                 3     0.00%           3                 3     0.00%           0                 0         -
timelock/src/error.rs                                          6                 2    66.67%           1                 0   100.00%           6                 2    66.67%           0                 0         -
timelock/src/lib.rs                                          649                46    92.91%          32                 2    93.75%         393                18    95.42%           0                 0         -
timelock/src/roles.rs                                        141                10    92.91%           6                 0   100.00%          76                 7    90.79%           0                 0         -
timelock/src/storage.rs                                      115                15    86.96%          12                 1    91.67%          68                 7    89.71%           0                 0         -
timelock/src/test.rs                                        1479                16    98.92%          37                 0   100.00%         531                 1    99.81%           0                 0         -
timelock/src/types.rs                                          3                 3     0.00%           3                 3     0.00%           3                 3     0.00%           0                 0         -
token-admin-registry/src/lib.rs                              368                23    93.75%          18                 1    94.44%         257                 4    98.44%           0                 0         -
token-admin-registry/src/test.rs                             825                 0   100.00%          21                 0   100.00%         287                 0   100.00%           0                 0         -
token-admin-registry/src/types.rs                              2                 2     0.00%           2                 2     0.00%           2                 2     0.00%           0                 0         -
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                      35839              2363    93.41%        1529               340    77.76%       19431              1430    92.64%           0                 0         -```

</details>

> Commit `382b2f92` | [Full CI run](https://github.com/smartcontractkit/chainlink-stellar/actions/runs/32134144585)

<!-- Sticky Pull Request Commentcontract-coverage -->