Desktop: Resolves #13586: Preserve scroll when switching between Markdown and Rich Text Editors

[personalizedrefrigerator]

Summary

This pull request restores the last scroll position when switching between the Markdown and Rich Text Editors. Previously, this scroll position was only restored when switching notes.

Fixes #13586.

Screen recording

Screencast.from.2025-10-31.08-52-40.webm

The above screen recording shows:

• Switching between notes with the Rich Text Editor enabled. The scroll position for each note is restored.
• Opening a longer note and scrolling to the end, then switching editors. In both, the note is initially scrolled to the end of the document.
• Scrolling to the top of a note in the Markdown editor, then switching to the Rich Text Editor. The Rich Text Editor is initially scrolled to the top of the document.

[vampyren]

Awesome! This has made me putt my hair a few times on long pages 👯