Forgejo uses /git/refs (plural) not /git/ref (singular), causing git.getRef() to 404. Use repos.getBranch() on Forgejo instead, which returns the same SHA data via a compatible endpoint. Also adds the tag mode workflow (.forgejo/workflows/claude.yml) for @claude mentions on issues, PR reviews, and label triggers. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>