feat(giveback): baseline /giveback page behind feature flag (Phase 1)

packages/shared/src/components/MainLayout.tsx

@@ -321,7 +321,11 @@ function MainLayoutComponent({
             <div
               className={classNames(
                 'relative flex min-h-0 flex-1 flex-col',
-                'laptop:overflow-hidden laptop:rounded-24 laptop:border laptop:border-border-subtlest-quaternary laptop:bg-background-default laptop:p-0.5 laptop:shadow-2',
+                // `overflow-clip` clips to the rounded card exactly like
+                // `overflow-hidden` but, unlike hidden, does not establish a
+                // scroll container, so descendant `position: sticky` elements
+                // (e.g. sticky tab bars) keep sticking to the viewport.
+                'laptop:overflow-clip laptop:rounded-24 laptop:border laptop:border-border-subtlest-quaternary laptop:bg-background-default laptop:p-0.5 laptop:shadow-2',
                 !hasTopBanners &&
                   !topBanner &&
                   'laptop:min-h-[calc(100vh-1.5rem)]',