fix: revert removeAllListeners() from destroyRoom() to stop SDK teardown errors

Closure guards on all 15 handlers already isolate React state from stale
rooms — the sledgehammer removeAllListeners() was stripping the SDK's own
internal listeners (PCManager, SignalClient), causing "Tried to add a track
for a participant that's not present" errors on rapid channel switches.

packages/web/src/hooks/useLiveKit.ts

@@ -107,10 +107,9 @@ function parseIdentity(identity: string): { userId: string; username: string } {
 
 let _connectGeneration = 0;
 
-/** Strip all listeners then disconnect — prevents ghost Room memory leaks. */
+/** Null-safe Room.disconnect() wrapper — lets the SDK tear down its own internals cleanly. */
 function destroyRoom(room: Room | null): Promise<void> | void {
   if (!room) return;
-  room.removeAllListeners();
   return room.disconnect();
 }