## Summary
Clear missing media validation errors after paste/drop media uploads by
emitting the existing widget-change event path.
## Changes
- **What**: Emit `node.onWidgetChanged` after image/video upload
completion updates the file combo widget.
- **What**: Emit the same widget-change path after Load Audio upload
completion.
- **What**: Add unit coverage for upload completion emitting
`onWidgetChanged` and for missing media clearing through that existing
hook path.
- **What**: Add E2E coverage for Load Image drag/drop and paste clearing
validation rings, with red/green verified from a fresh `main` base.
- **Dependencies**: None.
## Review Focus
Please check that paste/drop upload paths now reuse the existing
widget-change error-clearing path instead of expanding `widget.callback`
patching.
Also check the Load Image E2E helper path for synthetic paste/drop
behavior.
Supersedes #12207.
Ref: FE-687
## Screenshots
Before
https://github.com/user-attachments/assets/2cee52bc-b1c8-4dff-8a02-5b18a69ae639
After
https://github.com/user-attachments/assets/e1ecd147-1d8a-470e-b77d-13345d473ef3
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-12212-fix-clear-media-upload-errors-via-widget-change-35f6d73d365081bcb1a0dfc042d417eb)
by [Unito](https://www.unito.io)
95e616b894