fix(vision): unwrap fast_json list-wrapped object

apps/worker/worker_app/tasks/vision/vlm_fast_json.py

@@ -161,6 +161,13 @@ def call_fast_json(
         except json.JSONDecodeError:
             logger.warning("[vision.v2] fast_json JSON 解析失败 elapsed=%.1fs head=%s", elapsed, raw[:200])
             return None
+        if isinstance(obj, list):
+            # 模型偶发将对象包在数组里，取第一个 dict 元素
+            dicts = [x for x in obj if isinstance(x, dict)]
+            if not dicts:
+                logger.warning("[vision.v2] fast_json list 内无 dict: %s", type(obj))
+                return None
+            obj = dicts[0]
         if not isinstance(obj, dict):
             logger.warning("[vision.v2] fast_json 非 dict: %s", type(obj))
             return None