Add Pre-Commit Hooks to Block Non-Compliant Files

Per docs-doctrine Phase 5, non-compliant commits must be blocked at commit time. This complements CI checks by catching violations before they reach the remote.

Acceptance Criteria

• [ ] Install pre-commit framework (or equivalent git hook manager)
• [ ] Add hook that rejects files matching banned patterns (.bak, .old, _v2, etc.)
• [ ] Add hook that checks YAML front matter presence on managed file types
• [ ] Add hook that rejects naming convention violations (version suffixes, wrong casing)
• [ ] Add hook that flags derived files with stale hashes (if generation scripts exist)
• [ ] Document setup steps so any clone can activate hooks with one command