Cache the page-owned app response before starting the worker

frontend/lazy.js

@@ -122,6 +122,19 @@
       for (const type of ['pointerenter', 'focus', 'touchstart']) element.addEventListener(type, () => load(name).catch(() => {}), { once: true, passive: true });
     },
   };
+  // Own this response once. Classic-script and fetch preloads do not share
+  // their cached bodies in WebKit; the later bootstrap consumes this promise.
+  if(manifest.appCache && root.crypto?.subtle) {
+    api.appResponse=(async()=>{
+      const key=url('/app.js');
+      try {
+        const cache=await root.caches?.open('ytplayer-assets'), held=await cache?.match(key);
+        if(held?.headers.get('X-Asset-Hash')===manifest.files['/app.js']?.h && held)return held;
+      } catch {}
+      return root.fetch(key,{credentials:'same-origin'});
+    })();
+    api.appResponse.catch(()=>{});
+  }
   root.Lazy = api;
   root.navigator.serviceWorker?.addEventListener('message',event=>{
     if(event.data?.type==='ASSET_LAYOUT_REQUEST') event.source?.postMessage({type:'LAYOUT',value:api.layout});