Address PR review feedback on manage_native_filters:
- Wrap the user-controlled filter name and target column names as untrusted
content before returning them in the tool response, mirroring the
get_dashboard_info read path (prevents prompt-injection via filter metadata).
- Reject duplicate filter IDs in the update list so later updates for the same
filter are no longer silently dropped by the DAO's first-match resolution.
- Add docstrings to helper functions and type annotations to test helpers.
2a9bfc3ead