refactor(b2): eliminate all cross-plugin imports - contracts for worker/agent_runner/workstream, declared dependency for wiki

app/plugins/builtins/unified_search/contracts.py

@@ -50,6 +50,15 @@ class UnifiedSearchContract:
     simple_search = staticmethod(simple_search)
     BaseSearchProvider = BaseSearchProvider
 
+    @staticmethod
+    async def auto_register_providers(db: Any) -> None:
+        """Register providers for all active plugins (worker startup path)."""
+        from app.plugins.builtins.unified_search.provider_registry import (
+            auto_register_providers as _auto_register,
+        )
+
+        await _auto_register(db)
+
     @classmethod
     def get_function(cls, name: str):
         """Return a callable exposed by this contract, or None if absent."""