The mountEditor callback had content in its dependency array and was
used as a React ref callback. Every content change (keystroke) gave
mountEditor a new identity, causing React to destroy and recreate
the entire CodeMirror editor — losing cursor position, undo history,
and focus.
Remove content from the dependency array and use a separate useEffect
to push external content updates to the existing editor via
dispatch(). The editor is now only recreated when filePath, language,
or readOnly change.
Co-authored-by: Test User <test@example.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
