Incorrect key signature for transposing instrument shown at concert pitch when the part begins with a multimeasure rest

Issue type

Engraving bug (incorrect score rendering)

Description with steps to reproduce

1. Create a new score with a transposing instrument, e.g. Soprano Sax

2. Input a note anywhere except b.1.

3. Open the part and switch to concert pitch
   RESULT: The note is transposed correctly, but the key signature is incorrect

4. Still in the part, switch to transposed pitch

5. Turn off multimeasure rests (Ctrl+Shift+M)

6. Switch back to concert pitch
   RESULT: Both note and key signature are correct, as expected

Note: inputting music to b.1 rather than turning off MMRests at step 5 also causes the key signature to draw as expected.

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/57371eac-a51b-4bdd-9797-3ef5d78e7983

In which versions of MuseScore Studio is this issue present?

Nightly main

Regression

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

Operating system

Ubuntu 24.04.4 LTS

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