fix: Fix users unable to see or hear each other in voice channels due to

stale server sockets, passive non-initiators, and race conditions
during peer connection setup.

Fix users unable to see or hear each other in voice channels due to
stale server sockets, passive non-initiators, and race conditions
during peer connection setup.

Server:
- Close stale WebSocket connections sharing the same oderId in
  handleIdentify instead of letting them linger up to 45s
- Make user_joined/user_left broadcasts identity-aware so duplicate
  sockets don't produce phantom join/leave events
- Include serverIds in user_left payload for multi-room presence
- Simplify findUserByOderId now that stale sockets are cleaned up

Client - signaling:
- Add fallback offer system with 1s timer for missed user_joined races
- Add non-initiator takeover after 5s when the initiator fails to send
  an offer (NON_INITIATOR_GIVE_UP_MS)
- Scope peerServerMap per signaling URL to prevent cross-server
  collisions
- Add socket identity guards on all signaling event handlers
- Replace canReusePeerConnection with hasActivePeerConnection and
  isPeerConnectionNegotiating with extended grace periods

Client - peer connections:
- Extract replaceUnusablePeer helper to deduplicate stale peer
  replacement in offer and ICE handlers
- Add stale connectionstatechange guard to ignore events from replaced
  RTCPeerConnection instances
- Use deterministic initiator election in peer recovery reconnects
- Track createdAt on PeerData for staleness detection

Client - presence:
- Add multi-room presence tracking via presenceServerIds on User
- Replace clearUsers + individual userJoined with syncServerPresence
  for atomic server roster updates
- Make userLeft handle partial server removal instead of full eviction

Documentation:
- Add server-side connection hygiene, non-initiator takeover, and stale
  peer replacement sections to the realtime README

toju-app/src/app/infrastructure/realtime/peer-connection-manager/connection/negotiation.ts

@@ -60,6 +60,41 @@ export async function doCreateAndSendOffer(
   }
 }
 
+/**
+ * Replace a peer whose underlying connection is `failed` or `closed`.
+ * Returns the existing peer if still usable, or `undefined` after cleanup.
+ */
+function replaceUnusablePeer(
+  context: PeerConnectionManagerContext,
+  peerId: string,
+  reason: string
+): void {
+  const { logger, state } = context;
+  const peerData = state.activePeerConnections.get(peerId);
+
+  if (!peerData)
+    return;
+
+  const cs = peerData.connection.connectionState;
+
+  if (cs !== 'failed' && cs !== 'closed')
+    return;
+
+  logger.info('Replacing unusable peer', {
+    connectionState: cs,
+    peerId,
+    reason,
+    signalingState: peerData.connection.signalingState
+  });
+
+  try {
+    peerData.connection.close();
+  } catch { /* already closing */ }
+
+  state.activePeerConnections.delete(peerId);
+  state.peerNegotiationQueue.delete(peerId);
+}
+
 export async function doHandleOffer(
   context: PeerConnectionManagerContext,
   fromUserId: string,
@@ -70,6 +105,8 @@ export async function doHandleOffer(
 
   logger.info('Handling offer', { fromUserId });
 
+  replaceUnusablePeer(context, fromUserId, 'incoming offer');
+
   let peerData = state.activePeerConnections.get(fromUserId);
 
   if (!peerData) {
@@ -82,16 +119,15 @@ export async function doHandleOffer(
       signalingState === 'have-local-offer' || signalingState === 'have-local-pranswer';
 
     if (hasCollision) {
-      const localId =
-        callbacks.getIdentifyCredentials()?.oderId || callbacks.getLocalPeerId();
-      const isPolite = localId > fromUserId;
+      const localOderId = callbacks.getIdentifyCredentials()?.oderId ?? null;
+      const isPolite = !localOderId || localOderId > fromUserId;
 
       if (!isPolite) {
-        logger.info('Ignoring colliding offer (impolite side)', { fromUserId, localId });
+        logger.info('Ignoring colliding offer (impolite side)', { fromUserId, localOderId });
         return;
       }
 
-      logger.info('Rolling back local offer (polite side)', { fromUserId, localId });
+      logger.info('Rolling back local offer (polite side)', { fromUserId, localOderId });
 
       await peerData.connection.setLocalDescription({
         type: 'rollback'
@@ -211,6 +247,8 @@ export async function doHandleIceCandidate(
 ): Promise<void> {
   const { logger, state } = context;
 
+  replaceUnusablePeer(context, fromUserId, 'early ICE');
+
   let peerData = state.activePeerConnections.get(fromUserId);
 
   if (!peerData) {