Prevent modifications to protected files in governance policy

[github-actions]

A failure was detected and analyzed automatically.

Root cause: The automated agents incorrectly modified a protected file, violating the established governance policy.
Prevention: Implement a pre-commit hook that checks for modifications to protected files and prevents commits that violate the governance policy.

Original failure

PR #40: Weekly reflection: define Review Standards governance policy

Files: GOVERNANCE.md

Review feedback:
github-actions[bot]: This PR modifies protected files that agents must not change per GOVERNANCE.md:

• GOVERNANCE.md

Please remove these changes and resubmit.

[josephfusco]

Redundant. File Guard already prevents protected file modifications.