- Add 30s TTL leaderboard cache with invalidation on fight completion - Add scoreRound performance benchmark: 1000 rounds in <100ms - Add checkAnswer performance benchmark: 1000 checks in <50ms - Add adversarial regex backtracking test for checkAnswer - Verify SSE cleanup: connections, IP counters, spectator counts, event listeners all properly decremented in finally block on disconnect Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>