mathlib-fp 1.9.9 PR notes

Change boundary

This release branch completes the 1.9.9 convergence handoff without touching src/. The public interface digest of every unit must remain identical to the frozen 1.9 snapshot; the API snapshot check enforces that.

What changed

• Added the closed capability-manifest-1.10.0.json and its human-readable explanation.
• Added the final api-snapshot-final-1.9.9.json and API_SNAPSHOT_FINAL_1.9.9.md, and closed the routing language in the 1.9.3 candidate and diff documents.
• Added the provenance audit (provenance-audit-1.9.9.json) covering all 50 src/ units.
• Added the governance policies and updated SECURITY.md (security support window) and CONTRIBUTING.md (new-domain gate).
• Added tools/convergence.py, tools/check_convergence.py, and tools/test_convergence.py (20 focused unit tests).
• Integrated the convergence gate into tools/qualify_release.py, ci.yml (Linux, Windows, and checksummed clean-archive steps), release-qualification.yml, and RELEASING.md.
• Advanced release identity to 1.9.9: CHANGELOG.md, README.md, docs/versions.json, docs/capabilities.json, docs/index.md, docs/SUPPORT.md, the Lazarus package version, check_docs.py, the roadmap, and the documentation workflow.

Review checklist

• [ ] The closed manifest accepts exactly the roadmap 1.10.0 scope: TVector2D.Rotate plus the no-deprecation decision; everything else is explicitly deferred.
• [ ] The final snapshot diff is empty across source/behaviour/warnings/ packaging, and no src/ interface digest changed.
• [ ] Every unsupported capability-inventory family has a matching deferral record.
• [ ] Policies state testable commitments, not aspirations; the checker fails when the documents disagree.
• [ ] CI runs python tools/test_convergence.py and python tools/check_convergence.py on Linux and Windows and from the checksummed clean archive.

Verification commands

python tools/test_convergence.py

python tools/check_convergence.py

python tools/check_docs.py

python tools/test_release_state.py

git diff --check