Update styles in style.css to enhance layout and performance

- Added `contain: paint;` to the body for improved rendering performance.
- Changed `overflow` property from `visible` to `hidden` to prevent unwanted content overflow.

style.css

@@ -188,6 +188,7 @@ body {
   overflow: hidden;
   /* Own stacking context so heavy SVG repaints don’t fight the grid panel (paint isolation). */
   isolation: isolate;
+  contain: paint;
   z-index: 0;
   /* Drags were selecting compass/ring labels as text; map chrome isn’t meant to be selectable. */
   user-select: none;
@@ -198,7 +199,7 @@ body {
   display: block;
   width: 100%;
   height: 100%;
-  overflow: visible;
+  overflow: hidden;
   shape-rendering: optimizeSpeed;
   -webkit-user-select: none;
   user-select: none;