添加cadfs_to_cdsl代码，优化cad生成

backend/app/services/storage.py

@@ -96,6 +96,19 @@ class WorkspaceStore:
     def read_conversation(self, conversation_id: str) -> dict[str, Any] | None:
         return _read_json(self.conversation_path(conversation_id))
 
+    def clear_current_task_references(self) -> int:
+        """Detach conversations from task artifacts removed by a protocol reset."""
+        cleared = 0
+        for path in self.settings.conversation_root.glob("conv_*/conversation.json"):
+            record = _read_json(path)
+            if not isinstance(record, dict) or not record.get("current_task_id"):
+                continue
+            record["current_task_id"] = ""
+            record["updated_at"] = now_iso()
+            _write_json(path, record)
+            cleared += 1
+        return cleared
+
     def append_conversation_message(self, conversation_id: str, message: dict[str, Any], current_task_id: str | None = None) -> dict[str, Any]:
         record = self.ensure_conversation(conversation_id, current_task_id)
         known = {str(item.get("id") or "") for item in record["messages"] if isinstance(item, dict)}