Can't insert clefs in percussion stave after changing to pitched instrument

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

In percussion staves we cannot change the clef. However, after inserting a later instrument change to a pitched instrument (e.g. glockenspiel), we should be able to insert clefs as usual in the section after the instrument change. Currently, MuseScore forbids this. Also, if the clef created by the instrument change itself is accidentally removed, we cannot add it back.

Steps to reproduce:

1. Create a new score with a Mixed Percussion staff.
2. At some point after the beginning of the score, insert a Change Instrument text and choose Glockenspiel.
3. Attempt to drag a clef from the palette to a point on the score after the instrument change.
   Expected result: the clef is added to the score
   Actual result: the clef disappears

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/fa0ee591-44c6-4e67-ab09-59ef23ebbd67

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

4.5.2, also present in master

Regression

I was unable to check

Operating system

Windows 10

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