fix(app): keep model provider headers visible (anomalyco#44115)

Author: Brendonovich

packages/app/src/components/dialog-select-model.tsx

@@ -450,7 +450,7 @@ function ModelSelectorPopoverV2View(props: {
                 <For each={groups()}>
                   {(group) => (
                     <MenuV2.Group>
-                      <MenuV2.GroupLabel class="gap-2 px-3">
+                      <MenuV2.GroupLabel class="sticky top-0 z-10 gap-2 bg-v2-background-bg-layer-01 px-3">
                         <span class="min-w-0 truncate">{group.items[0].provider.name}</span>
                       </MenuV2.GroupLabel>
                       <MenuV2.RadioGroup value={props.current()}>