fix: add explicit pendingRooms cleanup before cleanupRoom in reject handler

[Copilot]

Addresses race condition in rejoin failure path where concurrent checks of pendingRooms could see stale state during cleanup.

Change

Add explicit this.pendingRooms.delete(id) before cleanupRoom() in the reject handler:

reject: (error: Error) => {
  console.error("Rejoin failed:", error);
  this.pendingRooms.delete(id);  // ← Added
  this.cleanupRoom(roomId, adaptor.crdtType);
  this.emitRoomStatus(id, RoomJoinStatus.Error);
},

While cleanupRoom() already deletes from pendingRooms internally, doing it first ensures proper ordering: any code checking pending state during cleanup will immediately see the room is no longer pending, preventing race conditions.

Matches pattern used in handleJoinError where explicit cleanup follows cleanupRoom.

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