fix(channel): assign S.room when joining voice room

public/app.js

@@ -101,7 +101,9 @@ async function joinVoice(room) {
   orientListener();
 
   await openSignaling(room);
+  S.room = room;
   S.connecting = false;
+  renderAll();
 }
 
 async function fetchIce() {
@@ -166,6 +168,7 @@ function handleSignal(msg) {
   switch (msg.type) {
     case 'hello': {
       S.myId = msg.id;
+      S.room = msg.room;
       for (const p of msg.peers) {
         S.peers.set(p.id, makePeerRecord(p));
         // deterministic initiator: lower id offers (no glare storm on join)