fix(ui): standardize scrollable areas (#2399)

docs/ai/context/ui-components.md

@@ -79,6 +79,21 @@ Responsive screen component that calculates canvas dimensions based on breakpoin
 
 **Props**: None | **Slots**: `default({ width, height })`
 
+### ScrollableArea
+
+Reka UI scroll area with shared light-mode and dark-mode scrollbar styles.
+The component forwards HTML attributes to the scroll-area root.
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `contentAsChild` | `boolean?` | `false` | Render the viewport content wrapper through the single default slot child |
+| `orientation` | `'vertical' \| 'horizontal' \| 'both'` | `'vertical'` | Scrollbar orientations to render |
+| `type` | `ScrollAreaRootProps['type']?` | `'auto'` | Reka UI scrollbar visibility behavior |
+| `viewportClass` | `string \| string[]?` | — | Classes for the Reka UI viewport |
+
+**Slots**: `default`
+**Exposed**: `viewport` (the native scroll owner. Reka UI hides its native scrollbar and renders the configured custom track.)
+
 ### Skeleton
 
 Loading placeholder with animation.