feat(matchmaking): add selectedGame support and implement exitMatchmaker to clear active tickets

Added selectedGame state and UI dropdown

Updated startQueue() to pass { game, mode } metadata

Added exitMatchmaker() to remove existing ticket

Stored active matchmaker ticket in context

Prevents duplicate matchmaker ticket errors

src/providers/NakamaProvider.tsx

@@ -39,6 +39,7 @@ export interface NakamaContextType {
   loginOrRegister(username: string): Promise<void>;
   logout(): Promise<void>;
   joinMatchmaker(gameMetadata: GameMetadata): Promise<string>;
+  exitMatchmaker(gameMetadata: GameMetadata): Promise<void>;
   joinMatch(matchId: string): Promise<void>;
 
   sendMatchData(matchId: string, op: number, data: object): void;
@@ -70,6 +71,7 @@ export function NakamaProvider({ children }: { children: React.ReactNode }) {
   const gameMetadataRef = React.useRef<GameMetadata | null>(null);
   const [session, setSession] = useState<Session | null>(null);
   const [socket, setSocket] = useState<Socket | null>(null);
+  const [matchmakerTicket, setMatchmakerTicket] = useState<string | null>(null);
   const [matchId, setMatchId] = useState<string | null>(null);
   const socketRef = React.useRef<Socket | null>(null);
 
@@ -212,10 +214,22 @@ export function NakamaProvider({ children }: { children: React.ReactNode }) {
     );
 
     gameMetadataRef.current = { game, mode };
+    setMatchmakerTicket(ticket.ticket);
 
     return ticket.ticket;
   }
 
+  async function exitMatchmaker(gameMetadata: GameMetadata) {
+    const socket = socketRef.current;
+    const game = gameMetadata.game;
+    const mode = gameMetadata.mode;
+    if (!socket) throw new Error("socket missing");
+
+    console.log(`[Nakama] Exiting Matchmaking... game="${game}" mode="${mode}"`);
+    if (matchmakerTicket) await socket.removeMatchmaker(matchmakerTicket);
+    setMatchmakerTicket(null);
+  }
+
   // ----------------------------------------------------
   // EXPLICIT MATCH JOIN
   // ----------------------------------------------------
@@ -284,6 +298,7 @@ export function NakamaProvider({ children }: { children: React.ReactNode }) {
         loginOrRegister,
         logout,
         joinMatchmaker,
+        exitMatchmaker,
         joinMatch,
         sendMatchData,
         onMatchData,