Feature: Make commit info panel's height persistent

[optimized-riyan]

I frequently navigate between the "histories" and "changes" tabs and the height of the commit preview panel always snaps back to the default. It is mildly inconvinient to resize the panel again & again with the activator only being 1px high.
Screencast from 2024-09-14 14-19-57.webm

[love-linger]

done. You can test it from latest build https://github.com/sourcegit-scm/sourcegit/actions/runs/10861302874

[optimized-riyan]

That was quick thanks!