feat: new workspace screen with sticky search combobox design

- Replace workspace setup dialog with full-screen new workspace route
- Restyle Combobox SearchInput to match CombinedModelSelector Level 2 design:
  borderless sticky search bar above scroll area instead of inline bordered box
- CombinedModelSelector now uses shared SearchInput, removing duplicate ProviderSearchInput
- Fix TooltipTrigger children type to accept render functions (remove PropsWithChildren wrapper)
- Fix empty rightControls View causing gap between dictation and send buttons
- Add branch picker with searchable Combobox and GitBranch icons
- Muted icon buttons (attachment, dictation, voice mode) that brighten on hover

packages/app/src/app/_layout.tsx

@@ -769,6 +769,7 @@ function RootStack() {
         <Stack.Screen name="h/[serverId]/index" />
         <Stack.Screen name="h/[serverId]/sessions" />
         <Stack.Screen name="h/[serverId]/open-project" />
+        <Stack.Screen name="h/[serverId]/new" />
         <Stack.Screen name="h/[serverId]/settings" />
         <Stack.Screen name="pair-scan" />
       </Stack.Protected>

packages/app/src/app/h/[serverId]/new.tsx

@@ -0,0 +1,21 @@
+import { useLocalSearchParams } from "expo-router";
+import { NewWorkspaceScreen } from "@/screens/new-workspace-screen";
+
+export default function HostNewWorkspaceRoute() {
+  const params = useLocalSearchParams<{ serverId?: string; dir?: string; name?: string }>();
+  const serverId = typeof params.serverId === "string" ? params.serverId : "";
+  const sourceDirectory = typeof params.dir === "string" ? params.dir : "";
+  const displayName = typeof params.name === "string" ? params.name : undefined;
+
+  if (!sourceDirectory) {
+    return null;
+  }
+
+  return (
+    <NewWorkspaceScreen
+      serverId={serverId}
+      sourceDirectory={sourceDirectory}
+      displayName={displayName}
+    />
+  );
+}