fix(arch-a2): deactivation cleanup - container services, search provider, hook deregistration, notification sync, task state, activation order

app/core/service_container.py

@@ -29,6 +29,14 @@ class ServiceContainer:
         """Check if a service is registered."""
         return name in self._services
 
+    def remove(self, name: str) -> None:
+        """Remove a service registration (no-op if absent).
+
+        Used by plugin deactivation hooks to clean up services they
+        registered during activation.
+        """
+        self._services.pop(name, None)
+
     async def initialize(self) -> None:
         """Initialize core services."""
         if self._initialized: