ci(release): enforce release-note policy

[lefoulkrod]

What changed

• document the organization release-note and Conventional Commit policy
• require every PR to add a validated user-facing fragment or explicitly opt out
• add a tested fragment validator and Keep a Changelog draft generator
• add a lightweight metadata workflow that reruns when PR titles, bodies, or labels change
• publish the exact reviewed docs/releases/<version>.md body instead of raw GitHub-generated notes

Why

Release notes should come from polished user-facing input captured with each change, while still allowing infrastructure-only work to declare an explicit, reviewable exclusion.

How it was tested

• release-note Node test suite and fragment validation
• Go formatting, module, vet, staticcheck, and actionlint checks
• all Go tests
• govulncheck

Release note

None: Adds contribution and release-process enforcement; CLI behavior is unchanged.