This adds a workaround for issue #12172 where the Write tool ignores
umask and creates files with hardcoded 0600 permissions.
The hook:
- Runs after Write/Edit tool operations
- Detects files with restrictive 0600 permissions
- Applies umask-respecting permissions (e.g., 0644 with umask 022)
- Includes comprehensive test suite with 15 test cases
Users can configure this hook in their settings to fix file permissions
until the underlying issue in the Write tool is resolved.