fix: stop Site timers from running after a product is closed

The grade check and the layout preview run on short timers. When the
item went to the cart inside that window, no product was open and both
threw in the customer's browser, which also failed the browser tests
intermittently. Each now returns when no product is open. The cart test
waits for the empty state, which is painted on the next animation frame.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/site-quality.js

@@ -88,6 +88,8 @@ let tAval=null;
 function agendaAvaliacao(){
   clearTimeout(tAval);
   tAval=setTimeout(()=>{
+    // o produto pode ter sido fechado nesses 220 ms (item foi para o carrinho)
+    if(!modo) return;
     const r=avaliar();
     const el=$('aoVivo');
     if(!el) return;