[Phase] Final verification and governed handoff

[edithatogo]

Native phase subissue for track #224. Canonical acceptance criteria and tasks are in conductor/tracks/post-release-security-quality-frontier_20260801/plan.md.

[edithatogo]

Completed by merged archival PR #231 (dfb907f): formal review recorded, all local gates passed, PR and updated-main hosted checks passed across the platform matrix and CodeQL, external Renovate/Codecov/publication gates remain explicit, and the track is archived.