feat: online-learning router persistence + auto-training via mome_store(query)

- MemoryRouter: save/load SGDClassifier state to disk (pickle + JSON)
- Router saves after every update(), loads on engine init
- MomeEngine.store_fact() accepts optional 'query' param → calls learn()
- extract_and_store() passes user query → trains router automatically
- mome_store tool schema: added optional 'query' parameter
- Router state persists across agent restarts in <store_dir>/_router/
- (router trained) indicator in mome_store response

__init__.py

@@ -65,6 +65,10 @@ MEMORY_STORE_SCHEMA = {
                 "type": "string",
                 "description": "The fact to remember.",
             },
+            "query": {
+                "type": "string",
+                "description": "Optional user query that triggered this fact. Used to train the router (query → expert mapping).",
+            },
         },
         "required": ["expert", "fact"],
     },
@@ -247,10 +251,12 @@ class MomeProvider(MemoryProvider):
     def _handle_store(self, args: Dict[str, Any]) -> str:
         expert = args.get("expert", "")
         fact = args.get("fact", "")
+        query = args.get("query", "")
         if expert in self._engine.experts and fact:
-            self._engine.experts[expert].write(fact)
+            self._engine.store_fact(expert, fact, query)
+            trained = " (router trained)" if query else ""
             return json.dumps({
-                "result": f"Stored in [{expert}]",
+                "result": f"Stored in [{expert}]{trained}",
                 "fact": fact,
             })
         return json.dumps({