feat: enhance review_changes with dynamic file requests

- Add instruction for Gemini to request files when needed
- Add comprehensive tests for files parameter functionality
- Test file request instruction presence/absence based on context
- Run all tests, ruff, and black formatting

Now review_changes can both accept context files and allow Gemini
to request additional files during review for better validation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

utils/git_utils.py

@@ -173,7 +173,7 @@ def get_git_status(repo_path: str) -> Dict[str, any]:
                 "rev-list",
                 "--count",
                 "--left-right",
-                f'{status["branch"]}@{{upstream}}...HEAD',
+                f"{status['branch']}@{{upstream}}...HEAD",
             ],
         )
         if success: