Keep the host form's Save working after Generate in the Media Library dialog

Problem/Motivation

After Generate in the Media Library dialog opened from a node form, the node form's Save stops working. It posts ?ajax_form=1 and shows "Oops, something went wrong." Edits are lost. Picking an existing item without Generate keeps Save working.

Cause: the Generate request is htmx, so core does not make ids unique, and the library's "Insert selected" renders as a plain #edit-submit whose ajax settings bind the node form's Save.

Steps to reproduce

1. Open a node add form with a media field.
2. Click Add media, then Generate with AI.
3. Click Generate, then Insert selected.
4. Click Save.

Proposed resolution

Render the htmx response with unique ids, as an AJAX request would, or scope the ajax settings it adds. Add a functional test.

Remaining tasks

• ✅ File an issue
• ❌ Addition/Change/Update/Fix
• ❌ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ✅ Update Release Notes
• ✅ Release

User interface changes

• Before (1.0.x): Save after Generate and Insert selected fails with "Oops, something went wrong".
  
• After: the article saves with the generated image.
  

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A

AI-Generated: Yes