- Added TSDoc for 'createHierarchicalValueFieldResolver'.
- Updated README with 'Extending the Schema' guide and Zabbix preconditions.
- Migrated all MQTT items to Agent 2 'mqtt.get' format across documentation and test data.
- Added 'docs/sample_import_distance_tracker_template.graphql' as a schema extension example.
- Verified all 38 tests pass.
