First pass at the new video tile designs

Here, I've begun updating the styles of video tiles to match the new designs. Not yet updated: the local volume option is supposed to go inside an overflow menu now, but I haven't gotten to that yet.

To make the outlines on hovered / speaking tiles show up properly, I have to remove the usePageFocusStyle hack, which was preventing CSS outlines from being used for anything other than focus rings. I honestly can't tell what problem it was solving in the first place: focus rings still appear to behave as expected throughout the application.

src/video-grid/BigGrid.tsx

@@ -957,7 +957,7 @@ function updateTiles(g: Grid, tiles: TileDescriptor<unknown>[]): Grid {
 }
 
 function updateBounds(g: Grid, bounds: RectReadOnly): Grid {
-  const columns = Math.max(2, Math.floor(bounds.width * 0.0045));
+  const columns = Math.max(2, Math.floor(bounds.width * 0.0055));
   return columns === g.columns ? g : resize(g, columns);
 }