feat：精简升级工作记忆模块

src/chat/heart_flow/observation/working_observation.py

@@ -31,18 +31,4 @@ class WorkingMemoryObservation:
         return self.retrieved_working_memory
 
     async def observe(self):
-        pass
-
-    def to_dict(self) -> dict:
-        """将观察对象转换为可序列化的字典"""
-        return {
-            "observe_info": self.observe_info,
-            "observe_id": self.observe_id,
-            "last_observe_time": self.last_observe_time,
-            "working_memory": self.working_memory.to_dict()
-            if hasattr(self.working_memory, "to_dict")
-            else str(self.working_memory),
-            "retrieved_working_memory": [
-                item.to_dict() if hasattr(item, "to_dict") else str(item) for item in self.retrieved_working_memory
-            ],
-        }
+        pass