- **Closed the 6 lines Codecov's patch-coverage check flagged as untested in `config/graphql/pipeline_settings_mutations.py`** once the `setup.cfg` include-path gap (see the companion fragment) let Codecov actually see this file. Two were genuine coverage holes with no prior test at all — `preferred_embedders` and `preferred_thumbnailers` had no test exercising a successful merge-and-preserve-siblings update through the mutation (only a negative wrong-component-type test existed for thumbnailers). The other four were the null-as-delete-marker branches for `preferred_enrichers`, `parser_kwargs`, and `component_settings`, which only had a test for the `preferred_parsers` case. Added `test_update_preferred_embedders_merges_and_preserves_siblings`, `test_update_preferred_thumbnailers_merges_and_preserves_siblings`, and null-value-deletes-entry tests for the other three fields in `opencontractserver/tests/test_pipeline_settings.py`.
