Enharmonic transposition by interval does not work correctly

Issue type

Engraving bug (incorrect score rendering)

Description with steps to reproduce

Enharmonic transposition by key (e.g. F# major to Gb major) works as expected, but by interval (diminished second) does not work correctly. See video below (00:13) - the notes are transposed, but not the key signature, nor the chord symbol.

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/259a2e56-27d2-41d9-bced-f6cd81d6703c

In which versions of MuseScore Studio is this issue present?

4.6.5 - latest main

Regression

No.

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

Start by reproducing the interval-based enharmonic transposition shown in the linked video, comparing it with transposition by key. Trace the code path responsible for interval transposition and inspect how it updates notes, key signatures, and chord symbols. Done means all three elements are rendered consistently after a diminished-second enharmonic transposition.