Fix the AI tabs overlapping in the Media Library in Claro, Gin and Default Admin

Problem/Motivation

In the Media Library the AI tabs ("Generate image with AI", ...) do not line up with the media type tabs: they miss the classes core gives every menu item (media-library-menu__item and the type class), so the admin theme's rules for the tab list do not apply to them. In Gin the AI tabs sit at a different height and the neighbouring tabs look overlapped.

Steps to reproduce

1. Use Gin, Claro or Default Admin as the administration theme.
2. Open the Media Library from a field that allows several media types.
3. Look at the tab list: the AI tabs have a different spacing, and the "New" badge makes them wrap onto two lines.

Proposed resolution

• Give each AI tab the same list item classes as its media type tab, plus its own -ai class.
• Keep the AI tabs at the height of the others, with the badge kept on the same line where it fits.
• Check Claro, Gin and Default Admin.

AI-Generated: Yes

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

• The AI tabs in the Media Library line up with the other tabs in Claro, Gin and Default Admin.

API changes

• None.

Data model changes

• None.

Release notes snippet

• The AI tabs in the Media Library no longer look overlapped.