Add Stationery and Stationery Dark themes with notebook chrome.

Manila folders, ruled chat, post-it nav, and folder tabs; dark variant uses Catppuccin Mocha colors with muted stickies and soft glows.

src/app/components/virtualizer/VirtualTile.tsx

@@ -11,7 +11,7 @@ export const VirtualTile = as<'div', VirtualTileProps>(
   ({ className, virtualItem, style, ...props }, ref) => (
     <div
       className={classNames(css.VirtualTile, className)}
-      style={{ top: virtualItem.start, ...style }}
+      style={{ top: virtualItem.start, zIndex: virtualItem.index, ...style }}
       data-index={virtualItem.index}
       {...props}
       ref={ref}