master is red: build ladder_bank_server in ladder-tests, and let the pre-flight expect it

[Yaraslaut]

Master is red

59788351 (#473) added a pre-flight to ladder-tests: every
scripts/scenario/scenarios/<name>/ must have a RungSpec and a server this
job builds. 1d690d5d (#470) then added bank's 22-scenario corpus and a
ladder_bank_server that deliberately is not a rung. The pre-flight fires on
master, naming bank — exactly as #473's own comment predicted:

::error::scripts/scenario/scenarios/bank/ is a corpus for 'bank', which is not
listed in examples/rungs.txt -- this job configures no ladder_bank_server for it.
Either list it there, or build its server in this job and extend this check to expect it.

The gate is working. A corpus with no server would otherwise have run five of
six directories and reported green — morph#462's defect one level down. This PR
takes the second branch the error names, rather than weakening the check or
adding bank to examples/rungs.txt (which would enrol bank in
wasm-ladder.yml's build loop, coverage.sh and codecov.yml's per-rung
components — a scope decision examples/rungs.txt and examples/LADDER.md
already settled the other way).

What changed

1. ladder-tests configures -DMORPH_BUILD_BANK_EXAMPLE=ON. That option
   alone guards add_subdirectory(examples/bank) in the root CMakeLists.txt;
   examples/bank/CMakeLists.txt then declares ladder_bank_server inside its
   own if(MORPH_BUILD_QT), which this job already sets. Nothing new to install:
   the apt step already names Lightweight's libsqlite3-dev, libyaml-cpp-dev,
   libzip-dev, unixodbc-dev, libsqliteodbc and libgl1-mesa-dev, and the
   server links only Qt6::Core + Qt6::WebSockets — qtwebsockets is already
   in the aqtinstall step's modules:.
2. The Build step names the target after the all-target build. A no-op when
   the flag is present; no rule to make target when someone drops it, rather
   than a silent absence surfacing as the scenario step's exit 2 a Qt build
   later.
3. The pre-flight gains a third arm — an addition, not a relaxation. A corpus
   that is neither a listed rung nor served by an
   add_executable(ladder_<name>_server) in examples/<name>/CMakeLists.txt
   still fails. The arm is keyed on that declaration, not on the literal name
   bank, so deleting the target makes the check fire again.
4. scripts/scenario/README.md's "In CI" section claimed CI does not run the
   corpus because no workflow builds the servers. False since ci: run the scenario corpus in ladder-tests, and let corpus changes reach it #473; rewritten to
   describe the pre-flight, the whole-corpus run, and the scripts/scenario/
   entry in the job's path filter.

Verification

Pre-flight run: script extracted from ci.yml with yaml.safe_load and run on
a clean checkout.

Before (at 1d690d5d) — exit 1:

::error::scripts/scenario/scenarios/bank/ is a corpus for 'bank', which is not listed in examples/rungs.txt -- this job configures no ladder_bank_server for it. Either list it there, or build its server in this job and extend this check to expect it.
ok: bookmarks -- corpus, RungSpec and ladder_bookmarks_server all accounted for
ok: kanban -- corpus, RungSpec and ladder_kanban_server all accounted for
ok: ledger -- corpus, RungSpec and ladder_ledger_server all accounted for
ok: pastebin -- corpus, RungSpec and ladder_pastebin_server all accounted for
ok: polls -- corpus, RungSpec and ladder_polls_server all accounted for
EXIT=1

After — exit 0:

ok: bank -- corpus, RungSpec and a local ladder_bank_server in examples/bank/CMakeLists.txt all accounted for
ok: bookmarks -- corpus, RungSpec and ladder_bookmarks_server all accounted for
ok: kanban -- corpus, RungSpec and ladder_kanban_server all accounted for
ok: ledger -- corpus, RungSpec and ladder_ledger_server all accounted for
ok: pastebin -- corpus, RungSpec and ladder_pastebin_server all accounted for
ok: polls -- corpus, RungSpec and ladder_polls_server all accounted for
EXIT=0

Still refuses an unknown corpus — scratch scripts/scenario/scenarios/nonesuch/:

::error::scripts/scenario/scenarios/nonesuch/ has no RungSpec in scripts/scenario/run_scenarios.py, so nothing can start a server for it and the driver would leave it out of its default set
EXIT=1

Still refuses bank if the target goes away — add_executable(ladder_bank_server …) commented out:

::error::scripts/scenario/scenarios/bank/ is a corpus for 'bank', which is neither listed in examples/rungs.txt nor served by an add_executable(ladder_bank_server) in examples/bank/CMakeLists.txt -- this job configures no ladder_bank_server for it. Either list it there, or declare that target and make this job configure and build it (see bank's -DMORPH_BUILD_BANK_EXAMPLE=ON below).
EXIT=1

The target actually builds. cmake --preset gcc-debug -DMORPH_BUILD_QT=ON -DMORPH_BUILD_LADDER=ON -DMORPH_LADDER_RUNGS=all -DMORPH_BUILD_BANK_EXAMPLE=ON → exit 0; full cmake --build --preset gcc-debug (469 targets) → exit 0:

build/gcc-debug/examples/bank/ladder_bank_server
build/gcc-debug/examples/bookmarks/ladder_bookmarks_server
build/gcc-debug/examples/kanban/ladder_kanban_server
build/gcc-debug/examples/ledger/ladder_ledger_server
build/gcc-debug/examples/pastebin/ladder_pastebin_server
build/gcc-debug/examples/polls/ladder_polls_server

Whole corpus, all six directories (run_scenarios.py --build-dir build/gcc-debug --rung bank …) — exit 0:

bank: 22 file(s) against ws://127.0.0.1:41991   (22 ok)
bookmarks: 14 file(s)                            (14 ok)
kanban: …  ledger: …  pastebin: 12  polls: 10
every scenario passed in: bank, bookmarks, kanban, ledger, pastebin, polls

Other job steps, unchanged and green:

• ctest --preset gcc-debug -L ladder -LE stress → 100% tests passed out of 1026
• bash scripts/check_automoc_includes.sh build/gcc-debug → 32 generated moc source(s), none ascending
• bash scripts/check_rung_filters.sh → All 39 rung-filter checks passed.
• bash scripts/ladder_rungs.sh ci-path-regex → byte-identical; neither of its
  inputs (examples/rungs.txt, scripts/ladder_rungs.sh) is touched.
• ci.yml parses with yaml.safe_load (17 jobs).

Not verified here: the run above used this machine's system Qt 6.11.2 and
GCC 16.2.1, not CI's aqtinstall Qt 6.8.1 on GCC 15 — the flags and target are
the same, but the exact CI toolchain combination is untested outside CI.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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