Show an error on the page when the Generate request fails

Problem/Motivation

When the Generate request fails in the browser (network error or non-2xx), the button comes back and the message is only announced to screen readers. A sighted editor sees nothing.

Steps to reproduce

1. Open a generator form.
2. Make the request fail, for example by going offline.
3. Click Generate.

Proposed resolution

Show the same message on the page next to the description, as the server-side error does.

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): a failed Generate request shows nothing on the page.
  
• After: the error shows below the description.
  

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A

AI-Generated: Yes