release: add curated notes and publication closure verification

[FernandoAbishai]

Summary

• add the single human-maintained CHANGELOG.md source and deterministic curated release-note rendering
• require an exact releaseTag changelog section only for publication; allow labeled Unreleased content for dry-runs
• add reusable live GitHub release closure verification with lightweight and annotated tag handling
• require explicit creator qualification declarations and retain closure JSON as Actions evidence only
• document the release lifecycle and preserve the exact six public release assets

Scope

Release-system scripts, workflow contracts, tests, and documentation only. No product/runtime/transcription/packaging/signing changes. Alpha.3 remains untouched; no tag or release was created.

Verification

• npm run smoke:release-notes
• npm run smoke:release-identity
• npm run smoke:release-metadata
• npm run smoke:public-release
• npm run smoke:release-workflow
• npm run smoke:published-release
• npm run smoke:runtime-contract
• npm run smoke:renderer-policy
• npm run smoke:model-manager
• npm run lint
• npm run build:frontend
• npm run smoke:backend
• python -m compileall -q backend
• git diff --check

Model-manager/backend tests required native loopback permission and passed outside the sandbox (8/8 and 54/54).

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