Give CPUs distinct personalities built on different poker libraries

Each CPU now thinks with one of four engines, each backed by a different
published library (pinned versions):

- montecarlo (@pokertools/evaluator): the existing balanced Monte Carlo
  equity player, moved to server/bots/montecarlo.js.
- calculator (poker-calculations): the library's decideAction over the
  table state; push/fold below 12BB via its jam breakeven equity.
  Skipped automatically if the native addon cannot load.
- range (poker-utils): tight player; preflop by hand-strength percentile,
  postflop equity vs an estimated opponent range, bluffs only when
  alpha/bluffEV say they pay.
- madehand (pokersolver): loose, sticky player that only looks at the
  made hand and draws.

server/ai.js assigns a mix of engines per table (makeStyles), falls back
to the Monte Carlo engine on errors, and legalizes every decision.
The engine and its parameters stay server-side; players cannot tell
which library a CPU uses. Tests cover every engine and the no-leak rule.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/bots/calculator.js

@@ -0,0 +1,86 @@
+'use strict';
+
+// 計算型: poker-calculations（ネイティブ実装）の decideAction に、勝率・ポットオッズ・コールの期待値から決めさせる。
+// スタックが少ないときは、同じライブラリのオールインの損益分岐勝率と比べてプッシュかフォールドにする。
+const { situation, CALL, FOLD, CHECK, passive, allIn, raiseToAmount, seedFrom, between } = require('./common');
+
+// ネイティブアドオンが読み込めない環境では、この思考は使わない
+let pc = null;
+try {
+  pc = require('poker-calculations');
+} catch {
+  pc = null;
+}
+
+const available = () => pc !== null;
+
+function randomStyle(rng) {
+  return {
+    // 小さいほどベット・レイズが多い（0.4 未満は無謀になり、0.6 を超えるとほとんどレイズしない）
+    aggressionThreshold: between(rng, 0.4, 0.52),
+    riskTolerance: between(rng, 0.4, 0.6), // 大きいほど薄い勝率でもコールする
+    raisePotFraction: between(rng, 0.55, 0.9), // ベット・レイズの大きさ（ポットに対する割合）
+    pushBias: between(rng, -0.04, 0.04), // プッシュの基準勝率への上乗せ（負ほど広くプッシュ）
+  };
+}
+
+const PHASES = ['preflop', null, null, 'flop', 'turn', 'river'];
+
+// decideAction に渡すテーブルの状態。他人の手札は空にする
+function tableState(hand, seat) {
+  const list = hand.list;
+  const index = (s) => list.findIndex((p) => p.seat === s);
+  const firstToAct = hand.board.length === 0 ? (index(hand.bbSeat) + 1) % list.length : 0;
+  return {
+    players: list.map((p, i) => ({
+      holeCards: p.seat === seat ? p.cards : [],
+      stack: hand.seats[p.seat].stack,
+      committedThisStreet: p.bet,
+      totalCommittedHand: p.committed,
+      folded: p.folded,
+      seat: i,
+    })),
+    communityCards: hand.board,
+    phase: PHASES[hand.board.length],
+    pot: hand.potTotal,
+    currentBet: hand.currentBet,
+    buttonSeat: index(hand.button),
+    smallBlind: hand.sb,
+    bigBlind: hand.bb,
+    actingIndex: index(seat),
+    lastRaiseIncrement: hand.state.lastRaiseAmount || hand.bb,
+    streetOpeningIndex: firstToAct,
+    // このストリートで動いた人（直前のアクションの表示はストリートが変わると消える）
+    actedThisStreet: list.map((p) => Boolean(p.last && p.last.type !== 'FOLD')),
+  };
+}
+
+function decide(hand, seat, { style, rng = Math.random, iterations = 500 } = {}) {
+  const s = situation(hand, seat);
+  if (!s) return null;
+  const { o, p, stack, bb, preflop, opponents, pot } = s;
+  const villains = Math.max(1, opponents);
+
+  // スタックが 12BB 以下ならプッシュかフォールド
+  if (preflop && stack + p.bet <= 12 * bb) {
+    const eq = pc.simulateHandOutcome(p.cards, [], iterations, seedFrom(rng), villains);
+    const breakeven = pc.pushFoldSymmetricBreakevenEquity(stack + p.bet, pot - p.bet);
+    if (eq >= breakeven + style.pushBias + 0.04 * (villains - 1)) return o.canRaise ? allIn(o) : CALL;
+    return passive(o);
+  }
+
+  const d = pc.decideAction(tableState(hand, seat), {
+    aggressionThreshold: style.aggressionThreshold,
+    riskTolerance: style.riskTolerance,
+    raisePotFraction: style.raisePotFraction,
+    monteCarloSimulations: iterations,
+    monteCarloVillains: villains,
+    rngSeed: seedFrom(rng),
+  });
+  if (d.action === 'raise' && o.canRaise) return raiseToAmount(hand, seat, hand.currentBet + d.raiseBy);
+  if (d.action === 'raise' || d.action === 'call') return o.canCheck ? CHECK : CALL;
+  if (d.action === 'check') return passive(o);
+  return FOLD;
+}
+
+module.exports = { decide, randomStyle, available };