Persist output types across save/load via hidden output_types widget

Types were lost on workflow reload because only key names were stored.
Now both keys and types are saved in hidden widgets and restored by
onConfigure, so colored connector dots persist without needing Refresh.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

json_loader.py

@@ -106,6 +106,7 @@ class JSONLoaderDynamic:
             },
             "optional": {
                 "output_keys": ("STRING", {"default": ""}),
+                "output_types": ("STRING", {"default": ""}),
             },
         }