Require release metadata updates before pull requests

[crankshift]

Summary

Require every pull request to update release metadata so merged changes trigger a new release tag build.

Context

The release tag workflow reads package.json after successful main checks and creates the matching vX.Y.Z tag. Pull requests that reuse an already-tagged package version can merge successfully but fail the release tag build.

Acceptance Criteria

• Contributor guidance says pull requests must update package.json version and CHANGELOG.md.
• Repo-local AI workflow guidance says PR creation requires package.json and CHANGELOG.md updates.
• A regression check protects the repo-local workflow guidance.

Notes

Keep this as process documentation and avoid adding another version bump beyond the current 0.5.7 release bump.