Incorrectly rendered border radius

## Bevy version

main

## What went wrong

From the `borders` example, the center yellow nodes should be circles but they get cut off on the right and bottom:

Start by running the `borders` example and compare its center yellow nodes with the attached image. Trace the border-radius rendering path used by that example; the work is done when those nodes render as complete circles without being cut off on the right or bottom.

Written by the indexing model from the issue text.