Promotion workflows for the release pipeline. promote-public publishes a tag to
the public repo's beta channel; promote-stable re-tags a finalised beta as a
stable vX.Y.Z. Both bound to the 'production' environment (required reviewer),
reading PUBLIC_REPO_SLUG/PUBLIC_REPO_TOKEN. Tree copy via scripts/promote.sh
excludes .git/.github so private CI never reaches the public repo.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>