Default clef doesn't update when changing part's default instrument

[CubikingChill]

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

Description

When changing the default instrument of a part, the clef doesn't update to match the new instrument's default clef.

Steps to reproduce

1. Create a new score with any instrument
2. Open the part's properties (right-click on part → Part Properties or similar)
3. Change the default instrument to one with a different clef (e.g., change from Violin (treble clef) to Cello (bass clef))
4. Observe that the clef in the score doesn't update

Expected behavior

The clef should automatically update to match the new instrument's default clef.

Actual behavior

The clef remains unchanged, requiring manual adjustment.

Version

4.7/Nightly

Additional context

This affects both master and 4.7 branches.

Supporting files, videos and screenshots

2026-03-15.21-46-11.-.Trim.mp4

In which versions of MuseScore Studio is this issue present?

4.7/Nightly

Regression

Yes, this works in the latest released version and is broken in the nightly builds

Operating system

Linux, but all systems should be affected.

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