fix: stabilize rpg publish and launch

src/App.tsx

@@ -32,6 +32,16 @@ const RpgRuntimeApp = lazy(async () => {
   };
 });
 
+function RuntimeLoadingFallback() {
+  return (
+    <div className="platform-ui-shell platform-viewport-shell platform-theme platform-theme--dark flex h-screen items-center justify-center bg-[image:var(--platform-body-fill)] p-4 font-sans text-[var(--platform-text-strong)]">
+      <div className="platform-subpanel rounded-2xl px-5 py-4 text-sm text-zinc-300">
+        正在启动
+      </div>
+    </div>
+  );
+}
+
 function isRpgRuntimeRoute(pathname: string) {
   const normalizedPath = normalizeAppPath(pathname);
   return (
@@ -126,7 +136,7 @@ export default function App() {
 
   if (isRuntimeActive) {
     return (
-      <Suspense fallback={null}>
+      <Suspense fallback={<RuntimeLoadingFallback />}>
         <RpgRuntimeApp
           initialIntent={runtimeIntent}
           onExitRuntime={() => {