feat: add leaderboard cache, performance benchmarks, and verify SSE cleanup

- 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>

server/src/routes/bots.ts

@@ -11,6 +11,14 @@ import { rateLimit } from '../middleware/rate-limit.js'
 
 export const botsRouter = new Hono()
 
+// Leaderboard cache — invalidated on fight completion
+const leaderboardCache = new Map<string, { data: unknown; expiresAt: number }>()
+const LEADERBOARD_TTL_MS = 30_000 // 30s cache
+
+export function invalidateLeaderboardCache() {
+  leaderboardCache.clear()
+}
+
 function hashSecret(secret: string): string {
   return createHash('sha256').update(secret).digest('hex')
 }
@@ -150,46 +158,58 @@ botsRouter.get('/:name', async (c) => {
 
 // Get bot stats -- full account page data
 
-// Season leaderboard endpoint
+// Season leaderboard endpoint (cached)
 botsRouter.get('/leaderboard', async (c) => {
   const seasonParam = c.req.query('season')
+  const cacheKey = seasonParam || '__alltime__'
+  const now = Date.now()
+
+  const cached = leaderboardCache.get(cacheKey)
+  if (cached && now < cached.expiresAt) {
+    return c.json(cached.data)
+  }
+
+  let result: unknown
 
   if (seasonParam === 'current' || seasonParam) {
     const { getCurrentSeason, getSeasonLeaderboard, getSeasonById } = await import('../engine/seasons.js')
     const season = seasonParam === 'current' ? getCurrentSeason() : getSeasonById(seasonParam)
     if (!season) return c.json({ error: 'Season not found' }, 404)
     const entries = await getSeasonLeaderboard(season.id)
-    return c.json({ season, entries })
+    result = { season, entries }
+  } else {
+    // All-time: fall through to default bot list sorted by Elo
+    const allBots = await db.select({
+      id: schema.bots.id,
+      name: schema.bots.name,
+      avatarSeed: schema.bots.avatarSeed,
+      archetype: schema.bots.archetype,
+      eloRating: schema.bots.eloRating,
+      wins: schema.bots.wins,
+      losses: schema.bots.losses,
+      winStreak: schema.bots.winStreak,
+      tier: schema.bots.tier,
+      botType: schema.bots.botType,
+    }).from(schema.bots)
+
+    const ranked = allBots.filter(b => b.botType !== 'classic')
+    ranked.sort((a, b) => b.eloRating - a.eloRating)
+
+    result = { season: null, entries: ranked.map(b => ({
+      botId: b.id,
+      botName: b.name,
+      archetype: b.archetype,
+      tier: b.tier,
+      wins: b.wins,
+      losses: b.losses,
+      eloRating: b.eloRating,
+      avatarSeed: b.avatarSeed,
+      winStreak: b.winStreak,
+    })) }
   }
 
-  // All-time: fall through to default bot list sorted by Elo
-  const allBots = await db.select({
-    id: schema.bots.id,
-    name: schema.bots.name,
-    avatarSeed: schema.bots.avatarSeed,
-    archetype: schema.bots.archetype,
-    eloRating: schema.bots.eloRating,
-    wins: schema.bots.wins,
-    losses: schema.bots.losses,
-    winStreak: schema.bots.winStreak,
-    tier: schema.bots.tier,
-    botType: schema.bots.botType,
-  }).from(schema.bots)
-
-  const ranked = allBots.filter(b => b.botType !== 'classic')
-  ranked.sort((a, b) => b.eloRating - a.eloRating)
-
-  return c.json({ season: null, entries: ranked.map(b => ({
-    botId: b.id,
-    botName: b.name,
-    archetype: b.archetype,
-    tier: b.tier,
-    wins: b.wins,
-    losses: b.losses,
-    eloRating: b.eloRating,
-    avatarSeed: b.avatarSeed,
-    winStreak: b.winStreak,
-  })) })
+  leaderboardCache.set(cacheKey, { data: result, expiresAt: now + LEADERBOARD_TTL_MS })
+  return c.json(result)
 })
 
 botsRouter.get('/:name/stats', async (c) => {