Harden seat transfer phrases (security review finding)

Three words from 32 was ~15 bits — enumerable within a code's
lifetime against an unthrottled endpoint. Now: 64-word list, 4-word
phrases (~24 bits / 16.7M combinations), a per-connection cap of 5
failed claims, and a global backstop that voids all pending codes and
cools the endpoint after 30 failures in 10 minutes. Codes stay
speakable; a brute force now gets ~35 guesses against 16.7M before
the door closes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/index.ts

@@ -36,6 +36,7 @@ interface Session {
   socket: WebSocket;
   playerId: PlayerId | null;
   roomId: string | null;
+  claimFails: number;
 }
 
 const sessions = new Set<Session>();
@@ -70,7 +71,7 @@ function broadcastRoomState(room: Room): void {
 }
 
 wss.on("connection", (socket) => {
-  const session: Session = { socket, playerId: null, roomId: null };
+  const session: Session = { socket, playerId: null, roomId: null, claimFails: 0 };
   sessions.add(session);
   send(socket, { type: "welcome", game: "wizwar" });
 
@@ -142,8 +143,15 @@ wss.on("connection", (socket) => {
           break;
         }
         case "claimTransfer": {
+          if (session.claimFails >= 5) {
+            return send(socket, { type: "error", message: "too many attempts on this connection — reconnect and mint a fresh phrase" });
+          }
           const result = claimTransferCode(String(msg.code ?? ""));
-          if ("error" in result) return send(socket, { type: "error", message: result.error });
+          if ("error" in result) {
+            session.claimFails++;
+            return send(socket, { type: "error", message: result.error });
+          }
+          session.claimFails = 0;
           send(socket, { type: "transferClaimed", seat: result });
           break;
         }