Add player stats, in-table ranking, host seating and review return

- Stats page (/stats): play style radar (TAG/LAG/rock/fish), VPIP, PFR,
  ATS, 3bet, WTSD, W$SD, WWSF, per-street fold rate, aggression
  frequency, hand win rate and net in BB, per table type, each with a
  bands-and-explanation sheet. Hands are counted per human player when
  they finish and stored as totals under data/stats/, keyed by a hash
  of the player ID (sent in a POST body, never in the URL).
- Ranking sheet at the table: everyone seated, ordered by stack or by
  net (stack minus buy-ins), updating live.
- The host can reorder seats by dragging (with a mini table preview and
  shuffle). Takes effect immediately between hands, otherwise at the
  start of the next hand; the dealer button stays with the same player.
- The full-session review opens in the same tab and its back button
  returns to the table it was opened from.

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

server/stats/summary.js

@@ -0,0 +1,55 @@
+'use strict';
+
+// 保存してある回数から、画面に出す割合を作る。テーブルの種類ごとと、すべてを合わせた合計（total）
+const { emptyBucket, MODES } = require('./store');
+
+const pct = (a, b) => (b > 0 ? Math.round((a / b) * 1000) / 10 : null);
+const sum = (xs) => xs.reduce((a, b) => a + b, 0);
+
+function merge(buckets) {
+  const out = emptyBucket();
+  for (const b of buckets) {
+    for (const [k, v] of Object.entries(b)) {
+      if (Array.isArray(v)) v.forEach((x, i) => (out[k][i] += x));
+      else out[k] += v;
+    }
+  }
+  out.netBB = Math.round(out.netBB * 100) / 100;
+  return out;
+}
+
+function view(b) {
+  return {
+    hands: b.hands,
+    won: b.won,
+    winRate: pct(b.won, b.hands),
+    vpip: pct(b.vpip, b.preflop),
+    pfr: pct(b.pfr, b.preflop),
+    ats: pct(b.ats, b.atsOpp),
+    atsOpp: b.atsOpp,
+    threeBet: pct(b.threeBet, b.threeBetOpp),
+    threeBetOpp: b.threeBetOpp,
+    sawFlop: b.sawFlop,
+    showdowns: b.showdown,
+    wtsd: pct(b.showdown, b.sawFlop),
+    wsd: pct(b.showdownWon, b.showdown),
+    wwsf: pct(b.wonSawFlop, b.sawFlop),
+    // ストリートごとの降りた割合（そのストリートで判断したハンドのうち）
+    fold: b.folds.map((f, i) => pct(f, b.seen[i])),
+    // アグレッション頻度: 全部の行動（フォールド・チェック・コール・ベット・レイズ）のうちベット・レイズ
+    afq: pct(sum(b.aggressive), sum(b.actions)),
+    afqStreets: b.aggressive.map((a, i) => pct(a, b.actions[i])),
+    netBB: b.netBB,
+    bb100: b.hands > 0 ? Math.round((b.netBB / b.hands) * 1000) / 10 : null,
+    hours: Math.round((b.ms / 3600000) * 10) / 10,
+  };
+}
+
+function summarize(data) {
+  const modes = {};
+  for (const m of MODES) modes[m] = view(data.modes[m] || emptyBucket());
+  modes.total = view(merge(MODES.map((m) => data.modes[m]).filter(Boolean)));
+  return { since: data.firstAt, modes };
+}
+
+module.exports = { summarize };