feat: improve the memory system

agent/memory/config.py

@@ -41,6 +41,10 @@ class MemoryConfig:
     enable_auto_sync: bool = True
     sync_on_search: bool = True
     
+    # Memory flush config (独立于模型 context window)
+    flush_token_threshold: int = 50000  # 50K tokens 触发 flush
+    flush_turn_threshold: int = 20  # 20 轮对话触发 flush (用户+AI各一条为一轮)
+    
     def get_workspace(self) -> Path:
         """Get workspace root directory"""
         return Path(self.workspace_root)