A Single Border and a Better Radius

I read the release notes. I just opened a Finder window and it feels better, and it took me a second to figure out why. It&rsquo;s two things. There&rsquo;s now a single vertical border between the sidebar and the content pane, so the two regions actually feel like two regions instead of one dark expanse where the divider was only implied by a shift in shade. And the inner corners got a slightly…