修复正式序列帧稳定引用持久化

正式序列帧强制携带 objectKey 与 assetObjectId，并按 objectKey 重建持久路径

同步收紧 External v1 OpenAPI 并补充签名 URL 负向测试

保留异步生成紧凑结果中的逐帧 assetObjectId 并更新架构文档

docs/openapi/genarrative-external-v1.openapi.json

@@ -4047,6 +4047,8 @@
         "type": "object",
         "required": [
           "imageSrc",
+          "objectKey",
+          "assetObjectId",
           "width",
           "height"
         ],
@@ -4055,16 +4057,14 @@
             "type": "string"
           },
           "objectKey": {
-            "type": [
-              "string",
-              "null"
-            ]
+            "type": "string",
+            "minLength": 1,
+            "description": "帧对应的稳定 OSS Object Key；服务端据此重建持久 imageSrc，不能只提交临时签名 URL。"
           },
           "assetObjectId": {
-            "type": [
-              "string",
-              "null"
-            ]
+            "type": "string",
+            "minLength": 1,
+            "description": "帧对应的稳定资产对象 ID。"
           },
           "width": {
             "type": "integer",
@@ -4076,7 +4076,7 @@
           }
         },
         "additionalProperties": false,
-        "description": "图片序列帧。数组位置是唯一播放顺序，不携带额外序号字段。"
+        "description": "图片序列帧。数组位置是唯一播放顺序，不携带额外序号字段；每帧必须同时携带 objectKey 与 assetObjectId，imageSrc 按 objectKey 规范化为持久站内路径。"
       },
       "EditorCharacterAnimationGenerationResponse": {
         "type": "object",