test: align downloader file contract stub

tests/test_downloader_path_mapping.py

@@ -210,6 +210,19 @@ def _load_transmission_module():
         def __init__(self, **kwargs):
             self.__dict__.update(kwargs)
 
+    class _DownloaderFile:
+        """隔离加载 Transmission 时提供下载器文件 DTO 的最小契约。"""
+
+        @classmethod
+        def model_validate(cls, value):
+            """按生产 DTO 入口把 SDK 对象投影为测试快照。"""
+            if isinstance(value, cls):
+                return value
+            payload = value if isinstance(value, dict) else vars(value)
+            instance = cls()
+            instance.__dict__.update(payload)
+            return instance
+
     class TorrentStatus(Enum):
         TRANSFER = "transfer"
         DOWNLOADING = "downloading"
@@ -271,6 +284,7 @@ def _load_transmission_module():
     schema_transfer_module.TransferTorrent = _TransferTorrent
     schema_transfer_module.DownloadingTorrent = _DownloadingTorrent
     schema_transfer_module.DownloaderTorrent = _DownloaderTorrent
+    schema_transfer_module.DownloaderFile = _DownloaderFile
     schema_dashboard_module.DownloaderInfo = object
     schema_types_module.TorrentStatus = TorrentStatus
     schema_types_module.TorrentQueryStatus = TorrentQueryStatus