Make app header sticky above content

index.html

@@ -136,11 +136,11 @@
 
     <div
       id="app"
-      class="fade-in flex min-h-screen flex-col px-4 py-8"
+      class="fade-in flex min-h-screen flex-col px-4 pb-8"
       data-sidebar-state="collapsed"
     >
       <!-- Header -->
-      <header class="ds-header mb-8 w-full">
+      <header class="app-shell__header ds-header mb-8 w-full">
         <!-- Logo -->
         <!-- Logo fades in once on initial load. -->
         <a