SHA-23: Stage 5 capability matrix and release-note rollup

[shaonianche]

Summary

Stage 5 (L) public-claims pass for Multica epic SHA-12 after stages 1–4 (C–J) landed on main.

• README capability matrix re-synced: PROFILE CORE/DOMAIN/FULL scopes, Activity/Workout/Course FILE_TYPE, post-edit PRESERVE/CANONICAL; new What this library still does not claim (non-goals + §11 residuals).
• Design doc current status, remaining-gaps (A–L), phase progress, O1 milestones, and §11 residual checklist updated — still not full Garmin FIT conformance marketing.
• Towncrier news/SHA-23.doc + epic rollup narrative docs/EPIC_SHA12_RELEASE_NOTES.md for the next version bump (no version bump in this PR).
• Fixture gap inventory + validation.py module docstring brought in line with shipped FILE_TYPE / scopes.

No new protocol features.

Acceptance (SHA-23)

• Matrix matches code
• Explicit remaining non-goals / residuals
• Epic can move to done / in_review with clear residual list (§11 checklist)

Test plan

• uv run pytest fit_tool/tests/test_public_api.py fit_tool/tests/test_validation.py fit_tool/tests/test_profile_scope.py -q (52 passed)
• Spot-check README matrix vs ProfileScope / IMPLEMENTED_FILE_TYPES on review

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[chatgpt-codex-connector]

Rewrite the fragment for release-note readers

When Towncrier builds the next release, this fragment will publish internal planning language such as “Stage 5,” “Multica SHA-12 / L,” “C–J,” and “§11” instead of concisely telling users what documentation or capability guidance changed. Rewrite it as a standalone user-facing description of the updated capability matrix and documented conformance limits.

AGENTS.md reference: AGENTS.md:L138-L138

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.72%. Comparing base (514ae61) to head (3856928).
✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Lines        2721     2721           
  Branches      461      461           
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  Hits         2523     2523           
  Misses        117      117           
  Partials       81       81           

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