frontend-app-api: expose root elements on specialized apps

Add an element shorthand to bootstrap and finalized app results so callers can render the root element without reaching through the tree instance.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

packages/frontend-defaults/src/createApp.tsx

@@ -17,7 +17,6 @@
 import { JSX, lazy, ReactNode, Suspense, useEffect, useState } from 'react';
 import {
   ConfigApi,
-  coreExtensionData,
   ExtensionFactoryMiddleware,
   FrontendFeature,
   FrontendFeatureLoader,
@@ -160,9 +159,7 @@ function PreparedAppRoot(props: {
   );
 
   if (!finalizedApp) {
-    return bootstrapApp.tree.root.instance!.getData(
-      coreExtensionData.reactElement,
-    )!;
+    return bootstrapApp.element;
   }
 
   const errorPage = maybeCreateErrorPage(finalizedApp);
@@ -170,7 +167,5 @@ function PreparedAppRoot(props: {
     return errorPage;
   }
 
-  return finalizedApp.tree.root.instance!.getData(
-    coreExtensionData.reactElement,
-  )!;
+  return finalizedApp.element;
 }