Use overflow clip in site layout

Use overflow clip instead of hidden in the page area of the site layout
to avoid creating a formatting context that would make sticky not work
as expected inside the page area.

packages/web_ui/src/index.css

@@ -27,7 +27,7 @@ body {
 }
 
 .site-layout {
-	overflow-x: hidden;
+	overflow-x: clip;
 }
 
 .site-layout-content-container {