Keep the Audio voice options when the settings form is saved

Problem/Motivation

Saving the AI Media settings form deletes the Audio voice option. The Editor options tab shows no voice control for Audio, and submitForm() replaces editor_options with what was posted.

Steps to reproduce

1. Save the AI Media settings form.
2. Open /media/add/audio?ai_media=1.
3. The voice option is gone.

Proposed resolution

Render the voice controls for Audio, and merge posted options into the stored ones instead of replacing them.

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): the Audio editor options have no voice settings.
  
• After: Audio shows the voice settings, and a save keeps them.
  

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A

AI-Generated: Yes