fix: make the toolbar always stable

Overview

This eliminates the need for the cssVariables hack and just always makes the toolbar stay at the top, except when growable is true

Uses a bit of css magic inline styles to force the overflow scrolling to only apply to the content div

note that scrolling is now fixed without having to adjust the editor configs

[ ] UI: works on smaller screen sizes
[ ] UI: feedback for any loading/error states
[ ] Check cancel/go-back flows
[ ] Check database state correct when deleting/updating (especially regarding relationships)
[x] changelog
[x] npm lint
[ ] no new deprecations