Adds the commit-msg hook promised in HOOKS.md since Round 5.
The hook auto-prepends the current Red Bear development phase
(e.g. 'phase 8.4:') to commit messages. The phase is detected
from the most recent 'phase X.Y:' commit in the git log.
Hook behavior:
- Normal commit → prepended: 'phase 8.4: my message'
- Already has prefix → skipped
- Revert message → skipped
- Empty/comment → skipped
Install: cp local/scripts/commit-msg .git/hooks/commit-msg && chmod +x
Updates HOOKS.md with:
- commit-msg hook documentation (install, behavior)
- Full tool inventory table (10 tools across 9+ rounds)
listing each tool's type, purpose, and modes/flags
