fix: supprimer le timer race timeout de 3 minutes

RACE_TIMEOUT = 180s eliminait tous les joueurs non qualifies apres 3min.
Le round se termine maintenant uniquement quand suffisamment de joueurs
se qualifient (ratio 60%).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

rolld_backend/game/src/rooms/ArenaRoom.js

@@ -5,7 +5,7 @@ const Chat = require("../chat/ChatManager");
 const LOBBY_TIMEOUT = 30;
 const COUNTDOWN_DURATION = 3;
 const ROUND_END_DURATION = 5;
-const RACE_TIMEOUT = 180;
+
 const QUALIFY_RATIO = 0.6;
 
 class ArenaRoom extends Room {
@@ -161,7 +161,6 @@ class ArenaRoom extends Room {
 
     console.log(`[ArenaRoom] Round ${this.state.roundNumber} started (race)`);
 
-    this._phaseTimer = setTimeout(() => this._endRaceTimeout(), RACE_TIMEOUT * 1000);
   }
 
   _endRound() {
@@ -205,17 +204,6 @@ class ArenaRoom extends Room {
     console.log(`[ArenaRoom] Game over — winner: ${winner}`);
   }
 
-  // ─── Race mode ──────────────────────────────────────────────────────
-
-  _endRaceTimeout() {
-    this.state.players.forEach((p, id) => {
-      if (!p.isQualified && !p.isEliminated) {
-        this._eliminatePlayer(id, "timeout");
-      }
-    });
-    this._endRound();
-  }
-
   // ─── Elimination helpers ─────────────────────────────────────────────
 
   _eliminatePlayer(sessionId, reason) {