fix: exclude transient image URLs from ImageCompare workflow serialization (#8715)

## Summary
Image URLs set by onExecuted are execution results that don't exist on
other machines. Disable workflow persistence (widget.serialize) while
keeping prompt serialization (widget.options.serialize) so compare_view
is still sent to the backend.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8715-fix-exclude-transient-image-URLs-from-ImageCompare-workflow-serialization-3006d73d365081b8aa87c7e05cb25f2f)
by [Unito](https://www.unito.io)

src/renderer/extensions/vueNodes/widgets/composables/useImageCompareWidget.ts

@@ -15,6 +15,10 @@ export const useImageCompareWidget = (): ComfyWidgetConstructorV2 => {
       ...options
     }) as IImageCompareWidget
 
+    // widget.serialize controls workflow persistence; widget.options.serialize
+    // controls prompt (API) serialization — only disable the former.
+    widget.serialize = false
+
     return widget
   }
 }