Unblock testing: message-your-sponsor entries, video pause-on-blur, tour polish

- Sponsor messaging is now reachable everywhere a new referral looks: a
  "Message your sponsor" card on My line, the Overview quick action, and a
  pinned "Message your sponsor" row atop the Messages drawer (even with no
  thread yet). Chat stores the sponsor from the dashboard.
- Watch-to-earn video + Shorts now PAUSE when the tab/window loses focus and
  resume on return, so a viewer must stay on the page for the watch to count.
- Welcome tour hides its frame on completion (no white about:blank panel).
  NOTE: rmcircle.team allows framing (frame-ancestors *); the blank was just
  the post-dwell blank state.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/assets/shorts.js

@@ -53,6 +53,13 @@
     $('shNext').hidden = false;
   }
   $('shNext').addEventListener('click', load);
+  // presence enforcement: pause when the tab/window loses focus, resume on return
+  document.addEventListener('visibilitychange', () => {
+    const v = $('shVideo'); if (!v || !v.src) return;
+    if (document.hidden) v.pause(); else if (!st.done) v.play().catch(() => {});
+  });
+  window.addEventListener('blur', () => { const v = $('shVideo'); if (v && v.src) v.pause(); });
+  window.addEventListener('focus', () => { const v = $('shVideo'); if (v && v.src && !st.done) v.play().catch(() => {}); });
   // tap the video to pause/resume
   $('shVideo').addEventListener('click', () => { const v = $('shVideo'); if (v.paused) v.play(); else v.pause(); });
   load();