Propagates the PreToolUse enforce-pr-target.sh backstop (byte-identical to
claridtimo/bang-game master) that denies any `gh pr create` not explicitly
aimed at claridtimo/*, guarding against accidental PRs on the greyhavens
upstream fork parent. Ships the 103-case regression battery and a CI job
(.github/workflows/hook-battery.yml) that gates it.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E3cmNbMM8gGpprBy8kcNuV
