iOS 1.0 RC 1: battery and heat work, version label, web player redraw tweaks

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

web/stems.js

@@ -87,6 +87,8 @@ export const Live = {
   get busy() { return !!this.current || this.pending.size > 0; },
   async poll() {
     clearTimeout(this.timer);
+    // Hidden tabs don't poll; coming back calls poll() again.
+    if (document.hidden) return;
     try {
       const r = await fetch(api("/api/queue"), { cache: "no-store", signal: AbortSignal.timeout(8000) });
       if (r.ok) {