Can't use Tab to navigate when vertical or horizontal frame is selected

Issue type

Accessibility issue (e.g. for keyboard-only or screen reader users)

Description with steps to reproduce

1. Select a vertical or horizontal frame
2. Press tab
3. See that nothing happens

Tab works on elements within frames (which are selectable via the 'Select next element in score' shortcut, Alt/Opt + Right arrow).

🚨 Note that once this is fixed, we should check that navigation order is correct for the properties of frames too.

Supporting files, videos and screenshots

Nothing to show; nothing happens

What is the latest version of MuseScore Studio where this issue is present?

Nightly

Regression

No.

Operating system

macOS 15

Additional context

No response

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible

The issue names no source file, test, or entry point. Start by reproducing the keyboard-navigation case with a selected vertical or horizontal frame; done means Tab moves focus or selection as expected, with navigation order also checked for frame properties.