Summary

Fixes the release step which was skipping on main with “not on main (on HEAD)”.

Root causes

1. Branch detection: git rev-parse --abbrev-ref HEAD returns "HEAD" in CI because the runner checks out a detached HEAD at a specific commit SHA. Fixed by comparing HEAD SHA against origin/main SHA.
2. anvil CLI not available: Docker container doesn’t have the anvil binary. Fixed by downloading it from anvil.fangorn.io/cli/download.
3. Idempotency check: git tag -l replaced with git rev-parse which is more reliable.

Test plan

• 560 tests pass
• Merge to main and verify release step creates tag + Anvil release