chore(hooks): add commit message normalizer

[marcus]

Summary

• add a repo-managed commit-msg normalizer that rewrites common legacy subjects into conventional commit format while preserving bodies and trailers
• install both pre-commit and commit-msg hooks via make install-hooks, including a linked-worktree-safe hook path
• align release/docs examples and add commit-msg smoke coverage

Testing

• make test-commit-msg
• go test ./...