fix firefox scrollbar from fractional split pane size

[Nixxx19]

fixes #4046

the iframe was inheriting fractional pixel dimensions from its flex parent (eg 787.5px), so the sketch inside (which sees an integer 788) overflowed by 0.5px and triggered a scrollbar in firefox/brave.

floored the iframe width and height via a ResizeObserver on its parent and added display: block. tested locally in brave, scrollbar is gone, chrome unchanged.

[yugalkaushik]

@Nixxx19 I tested your PR locally and the scrollbars still exist. I checked on Brave and the issue is still present. On Chrome, there were no scrollbars before and there are still none.
Also, if you make any further changes, please share a preview as well.

Brave Preview:

[Nixxx19]

hey @yugalkaushik thanks for testing and sorry for not attaching a screenshot earlier. just pushed a fix, tested locally in brave and the scrollbar is gone, screenshot attached. mind giving it another try?

[yugalkaushik]

@Nixxx19 I tested it locally and everything looks clean now. When you get some time, could you please test it on Firefox as well so we can confirm the issue is fixed once and for all? I’ll approve the PR after you verify it there.

[yugalkaushik]

I tested it on firefox and it works. @Nixxx19 Thank you for the amazing work.
@ksen0 This PR can be merged.

[ksen0]

Thanks both!