F0: establish task backend input and native job spine

backend/services/background_tasks/service.py

@@ -44,7 +44,7 @@ class TaskService:
         self._listeners.clear()
         self._jobs.clear()
 
-    async def submit(self, *, assistant_id, conversation_id, tool, instruction, invocation_id):
+    async def submit(self, *, assistant_id, conversation_id, instruction, invocation_id, backend=None, tool=None):
         if not self.runtime:
             raise ValueError("后台任务服务尚未启动")
         if not assistant_id or not conversation_id:
@@ -52,15 +52,25 @@ class TaskService:
         text = instruction.strip()
         if not text or len(text) > 12000:
             raise ValueError("任务指令必须为 1-12000 个字符")
-        if tool.type != "task":
-            raise ValueError("请选择后台任务工具")
+        if backend is not None:
+            if backend.type != "opencode":
+                raise ValueError("该任务后端尚未接通")
+            backend_id = backend.id
+            connection = deepcopy(backend.config)
+            connection["_backend_type"] = backend.type
+            secrets = deepcopy(backend.secrets)
+        else:
+            # F0 transition: retired when saved Tool bindings migrate in F1.
+            if tool is None or tool.type != "task":
+                raise ValueError("请选择任务后端")
+            backend_id, connection, secrets = tool.id, deepcopy(tool.definition["config"]), deepcopy(tool.secrets)
         async with self._submit_lock:
             record = await self.repository.create(TaskRecord(
                 id="task_" + uuid4().hex,
                 assistant_id=assistant_id, conversation_id=conversation_id,
-                tool_id=tool.id, instruction=text,
+                tool_id=backend_id, instruction=text,
                 origin_key=f"{conversation_id}:{invocation_id}"[:256],
-                connection=deepcopy(tool.definition["config"]), secrets=deepcopy(tool.secrets),
+                connection=connection, secrets=secrets,
             ))
             if not record.job_id and record.status == "queued":
                 await self._dispatch(record)