chore: migrate off the planning/ convention

[lesnik512]

Migrates lite-bootstrap off the planning/ convention and onto PR-body-as-spec, with CONTEXT.md owning the vocabulary and docs/adr/ holding rejected alternatives. Part of modern-python/.github#67.

This branch also carries chore(context7): drop the stale planning/ exclusion — the context7.json entry naming planning/ only becomes dead once this migration deletes the directory, so the two land together.

Replaces the two-axis planning/ + architecture/ convention with PR-body-as-spec,
CONTEXT.md for vocabulary, and docs/adr/ for rejected alternatives, per
modern-python/.github#67.

• planning/ deleted in full, 51 files. changes/ held 21 design records whose
  content is the diff each describes, and git history is that record; audits/
  and retros/ recorded two audit arcs that shipped complete (3 criticals, 5
  design issues, 7 refactors, 8 test gaps, 10 low-priority items across fix: honor root_path in offline-docs redoc handler #89-refactor: rename OpentelemetryConfig → OpenTelemetryConfig; FreeBootstrapperConfig → FreeConfig #103
  and refactor: replace InstrumentNotReadyWarning with is_configured classmethod + summary log #107; all 26 findings of the second audit across fix: lifecycle & teardown correctness (PR1 of bug-audit-v2) #108-chore: hygiene + CI gate (PR3 of bug-audit-v2) #110), so nothing
  there is outstanding; specs/ and plans/ held one org-wide README
  standardization whose lite-bootstrap half is in README.md today. releases/
  held ten notes: 1.4.0 and 1.3.0 diffed byte-identical against gh release view apart from a trailing newline GitHub adds, and 1.1.0 differs only where
  the local copy was edited after publication to chase a planning/ path rename —
  the Releases are the record either way.
• deferred.md's three items plus two never-scheduled findings from the second
  audit's scope appendix are drafted as issue bodies in
  ../DRAFT-ISSUES-lite-bootstrap.md, each carrying its revisit trigger. Not
  opened on GitHub.
• planning/decisions/ held four records; the previous, interrupted attempt at
  this migration had carried only two of them across. All four are now ADRs,
  frontmatter stripped: keep-per-instrument-axis is 0002, teardown-marker limits
  is 0003 (its "Update (1.4.0)" section kept as prose), orjson-opt-in is 0005,
  otlp-http-exporter-shape is 0006. None of the four declared a supersedes or
  superseded_by relationship, so none was lost in the strip. Four more ADRs
  rescue rejections that were buried in change files: 0001 (FastMCP teardown via
  a Provider lifespan rather than app._lifespan), 0004 (trace-exclusion stays one
  method), 0007 (the zero-dependency core was attempted and failed on pydantic's
  TypedDict rule under Python < 3.12), 0008 (the structlog->Sentry seam keeps its
  startswith heuristic rather than gaining a marker key). All eight keep a
  revisit trigger.
• architecture/ carried five prose pages. Three claims in them were enforceable
  and are now INVARIANT tests; the rest was mechanism readable from
  lite_bootstrap/ and is deleted, not relocated.
  test_importing_lite_bootstrap_needs_only_the_stdlib_and_typing_extensions
  (new tests/test_core_import_surface.py) walks every module's top-level AST and
  fails on a third-party import outside an import_checker or TYPE_CHECKING
  guard — the invariant that broke four times and the one this library actually
  controls in the free-threading story. Verified: an unguarded import orjson
  in logging_factory.py fails it, and adding a new guarded optional import plus
  a new stdlib import leaves it green.
  test_every_framework_config_post_init_cascade_reaches_base_config (new
  tests/test_config_cascade.py) spies on BaseConfig's terminator while
  constructing each framework config. Verified against the exact bug that
  shipped once: dropping CorsConfig's super().post_init() call fails it for
  FastAPIConfig and LitestarConfig, and giving SwaggerConfig a new post_init
  that does call super() leaves it green.
  test_only_the_silent_skip_path_lands_in_skipped_instruments
  (tests/test_free_bootstrap.py) pins the asymmetry CONTEXT.md defines "skipped"
  by. Verified: appending the dependency-missing case to skipped_instruments
  fails it, while adding another config-skipped instrument to FreeBootstrapper —
  the list legitimately growing — leaves it green.
  The free-threading page was judged to hold no enforceable claim of its own: its
  support matrix is a statement about upstream wheel availability, and its
  single-threaded-init section is a design stance, not a testable one. Its two
  live blockers are drafted as issues instead.
• CONTEXT.md was written by the interrupted attempt and audited rather than
  trusted. Its "Skipped" entry claimed both skip paths appear in
  build_summary(); a dependency skip appears in neither list, and the entry is
  corrected — the same claim the new invariant test now holds. All five Avoid
  entries were audited against real usage and all five earn their listing:
  "instrumentation" and "integration" appear only in their sanctioned senses
  (opentelemetry-instrumentation-* packages and the middleware named after them;
  docs/integrations/ and Sentry's own Integration objects), with one straggler —
  docs/introduction/quickstart.md said "production instrumentation" for what are
  mostly not instrumentation at all, now "production observability". That is a
  user-visible string on the docs site.
• README.md's extras paragraph linked architecture/free-threading.md and claimed
  no mandatory runtime dependencies. Both are fixed: the free-threading facts a
  user needs are inlined, and core's one dependency is named. That paragraph is
  user-visible on PyPI, and the old claim is what ADR-0007 exists to correct.
• AGENTS.md gains Workflow and Where-a-fact-goes and loses the planning lanes,
  the architecture/ promotion rule, and the capability index. The admission check
  applied to itself cut eight invariant bullets and four convention bullets that
  restated a docstring, a comment already at the site, pyproject.toml or the
  justfile — the frozen/non-frozen split Python enforces on its own, the
  slots-and-bare-super comment that sits three lines above the code it explains,
  the from_dict/from_object asymmetry both docstrings state. What survives is the
  three rules invisible in the code that obeys them, and the ty suppression
  spellings the justfile does not give.
• mkdocs.yml excludes /adr/ from the published site, matching modern-di: an
  internal decision record is not user documentation, and mkdocs --strict fails
  on a docs/ file absent from nav.
• justfile and lint-ci drop index and check-planning (there was no check-links
  recipe); the offline lychee gate in _checks.yml replaces them
  (Add the offline link gate to the 18 green repos, and unpublish the ADRs in the two that have them .github#66). Locally it went from 8 errors to 0 over 57 unique
  links — every one of the eight lived inside planning/, and deleting it is what
  made them green.

Beyond the recipe, and the reason this is chore: and not docs: release.yml read
the Release body from planning/releases/.md and hard-required one for every
stable tag, so deleting planning/ would have failed every future stable release.
It is now byte-identical to modern-di's post-migration workflow apart from the
PyPI project name, using GitHub's generated notes; modern-di dropped the same
gate in 1ea74ee (modern-python/modern-di#449). This retires the
mandatory-curated-notes policy; a release wanting prose is edited after the fact
with gh release edit.

Verification: just lint-ci clean, just test 242 passed at 100% coverage, just
docs-build strict clean, lychee --offline 0 errors, and no remaining reference to
planning/, architecture/, check-planning, check-links or convention-version
anywhere in the tree.

The sibling commit on this branch deletes planning/, so the exclusion now
names a directory that does not exist.

Dropping the key rather than leaving an empty list: Context7's schema
(https://context7.com/schema/context7.json) declares no required properties
and gives excludeFolders a default of [], so an absent key and an empty list
are equivalent. Absent matches the repos that never carried the line.

Verification

• just lint-ci — clean (eof-fixer, ruff format, ruff check, ty).
• Test suite green at the repo's 100% coverage gate.
• Offline link gate (lychee --offline --no-progress '**/*.md') — 0 errors.
• No planning/, architecture/, check-planning, check-links or convention-version reference remains.

Note

release.yml previously read planning/releases/<tag>.md, both as a hard gate for stable tags and as the Release body source; deleting planning/ without changing it would have broken the next stable release. It now uses GitHub's generated notes, matching modern-di post-modern-python/modern-di#449. This retires the mandatory-curated-notes policy.