B6 fix: error事件只在重试耗尽时推送

重试中也推error会让前端FatalErrorBanner误报生成失败,
应只在exhausted(彻底失败)时推error事件。

import OK

backend/app/workers/tasks.py

@@ -152,8 +152,9 @@ def run_generation_pipeline(self, task_id: int) -> dict:
                 db.commit()
         except Exception:
             pass
-        _push_event_sync(task_id, workspace_id, "error", {"code": 50001, "message": str(exc)}, seq + 1)
         if exhausted:
+            # 彻底失败才推 error(前端弹 FatalErrorBanner);重试中不推,避免误报"生成失败"。
+            _push_event_sync(task_id, workspace_id, "error", {"code": 50001, "message": str(exc)}, seq + 1)
             return {"task_id": task_id, "status": "failed", "error": str(exc)}
         raise self.retry(exc=exc)
     finally: