fix: stabilize rpg publish and launch

src/components/rpg-runtime-shell/RpgRuntimeShell.tsx

@@ -25,6 +25,16 @@ const RpgRuntimeOverlayHost = lazy(async () => {
   };
 });
 
+function RuntimeLayerLoadingFallback({ label }: { label: string }) {
+  return (
+    <div className="pointer-events-none fixed inset-x-0 top-4 z-[24] flex justify-center px-4">
+      <div className="rounded-full border border-white/10 bg-black/55 px-4 py-2 text-xs text-zinc-200 shadow-[0_12px_30px_rgba(0,0,0,0.32)] backdrop-blur-sm">
+        {label}
+      </div>
+    </div>
+  );
+}
+
 /**
  * RPG 运行态总外壳。
  * 这里承接运行时主布局、画布舞台、主阶段路由和 overlay host，
@@ -167,7 +177,7 @@ export function RpgRuntimeShell({
       }}
     >
       {gameState.worldType ? (
-        <Suspense fallback={null}>
+        <Suspense fallback={<RuntimeLayerLoadingFallback label="正在加载场景" />}>
           <RpgRuntimeCanvasStage
             gameState={gameState}
             visibleGameState={visibleGameState}
@@ -275,7 +285,7 @@ export function RpgRuntimeShell({
       />
 
       {gameState.worldType ? (
-        <Suspense fallback={null}>
+        <Suspense fallback={<RuntimeLayerLoadingFallback label="正在加载界面" />}>
           <RpgRuntimeOverlayHost
             gameState={gameState}
             isLoading={isLoading}