feat(levels): gate the dead turn, and state the curve instead of hoping for it

Round 1 played all fifty levels and came back with the mechanics clean and one
complaint repeated across the reports: 短暂以为转错了方向 — a turn that changed
nothing. That one is mechanical rather than perceptual, so it can be gated.

The first attempt gated `doubleDead`, and it was wrong. That counts dead states,
which scales with the state space: three-turn levels have ~187 reachable stuck
states and five-turn ones ~739, so a raw count made deep levels look eight times
worse when the rate is 2% against 5%. It would have erased every level past
three turns — the opposite of the brief, where turning is the signature and is
not to be rationed. The gate is `maxDeadTurns`, the longest run of turns before
something opens, at 1: one beat of suspense, then a release. Eleven of the fifty
shipped at 2.

Selection could not express the curve either. Spreading picks evenly over the
ranked pool returns whatever the pool is made of, and the pool is 88%
three-turn, so no weighting moved the distribution off {3: 46}. A quota per
depth states the curve outright, deepest first so the scarce end picks before a
family cap is spent on levels the shallow end has hundreds of.

Same rule bot, both sets: blind rotations 0.24 → 0.12, worst blind streak 4 → 1,
decisions unchanged at 10.3. The same amount to do, half the wasted motion.
Rotation now runs 1.8 / 3.0 / 4.1 across the bands against 1.8 / 3.0 / 3.5.

Verdicts are keyed by the board rather than by its id, because a reselect
re-issues ids from the ordinal and `c50-01-v05` is not the same board before and
after — the review sheet was one reselect away from printing one level's verdict
under another's thumbnail.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/level-board.html

@@ -162,7 +162,7 @@ footer{margin-top:56px;padding-top:20px;border-top:1px solid var(--rule);color:v
 <li class="done"><div class="t"><span class="tid">T1.2</span><span class="tt">解除 rotations===3 的硬限制，允许 4/5/6+</span><span class="tag good">完成</span></div></li>
 <li class="done"><div class="t"><span class="tid">T1.3</span><span class="tt">反差感指标进 deepLevelStats 并作门槛</span><span class="tag good">完成</span></div><div class="note">contrastStats 已进 deepLevelStats 并作门槛；实测 weave 22–33、switchback 29、spiral 18–24、orbits 12–17，petals 仅 2.0–5.7、crossing 3.8–5.5</div></li>
 <li class="done"><div class="t"><span class="tid">T1.4</span><span class="tt">每转释放 ≥2 枚的门槛</span><span class="tag good">完成</span></div><div class="note">改为按朝向配额插棋（每个朝向 ≥2 枚在等），取代原来的随机比例——随机比例会留下空转的朝向</div></li>
-<li class="doing"><div class="t"><span class="tid">T1.5</span><span class="tt">扩产到 ≥120 候选并去重、家族均衡</span><span class="tag live">进行中</span></div><div class="note">候选池已达 235 关（深度 {3:165,4:46,5:22,7:2}），正用含开局展示位的构造重扫</div></li>
+<li class="doing"><div class="t"><span class="tid">T1.5</span><span class="tt">扩产到 ≥120 候选并去重、家族均衡</span><span class="tag live">进行中</span></div><div class="note">扩产到 400 种子（8 片并行）。目的不是多，是为了付得起两道新闸门的代价：双向死转态 ≤2 只留 16%，在 94 个候选上会只剩 8 关</div></li>
 <li class="blocked"><div class="t"><span class="tid">T1.6</span><span class="tt">终局三枚互锁（hero+gate+tail）</span><span class="tag bad">受阻</span></div><div class="note">深关卡的主要死因：5 转以上有 60% 死在「终局单出口」。实测终局是锁链自己的三枚棋子在 6 个朝向里堵死 5 个。双向释放约束只覆盖了 hero/tail 两枚，三枚组合覆盖不到——这是可达状态的性质，构造时难保证。当前对策是提高扫描量靠筛选拿到，不是修构造</div></li>
 <li class="done"><div class="t"><span class="tid">T1.7</span><span class="tt">开局展示位（快速爽到）</span><span class="tag good">完成</span></div><div class="note">实测整个构造的开局中位只有 2 枚可点、最佳演出 0.57s——锁链开局全锁死。在构造里预留 2 个开局位（立即可点且路线长到值得看），实测开局可点 2→3 枚、最佳演出 0.72s→1.12s</div></li>
 <li class="done"><div class="t"><span class="tid">T1.8</span><span class="tt">离场演出封顶</span><span class="tag good">完成</span></div><div class="note">计时原本线性无上限，最长一次 17.4s，正式关 18.8% 超过 2s。拐点 2.4s 以下完全不变，以上加速逼近 3.2s 上限。labs/exit-timing 可同步对比</div></li>
@@ -182,7 +182,7 @@ footer{margin-top:56px;padding-top:20px;border-top:1px solid var(--rule);color:v
   <h3><span class="pid">P3</span>迭代：跑几轮把曲线调平</h3>
   <ul class="tasks">
   <li class="done"><div class="t"><span class="tid">T3.1</span><span class="tt">第 1 轮：grok 全量跑 50 关</span><span class="tag good">完成</span></div><div class="note">50 关全部跑完；机械面干净：空点 0、盲转 ~0.3/关、全部通关。总体读数：整批偏易一档（2 分 vs 刚好的 3 分）</div></li>
-<li class="doing"><div class="t"><span class="tid">T3.2</span><span class="tt">按实测曲线调整选关，重选</span><span class="tag live">进行中</span></div><div class="note">按 R1 唯一可用的总体读数「偏易」调整：扩池到 400 种子后把旋转深度整体上推，而不是按关排名重选</div></li>
+<li class="doing"><div class="t"><span class="tid">T3.2</span><span class="tt">按实测曲线调整选关，重选</span><span class="tag live">进行中</span></div><div class="note">R1 唯一可用的是总体读数「偏易」，不是逐关排名。据此定的 R2 改动只有一条、且是机械可测的：给 doubleDead（左右转都打不开任何棋子的可达卡住态）设闸门——它此前完全没设，当前 50 关中位 4、最高 27。这正是用户说的「无效转动就会很无聊」，也是 agent 后段反复写的「短暂以为转错了方向」</div></li>
 <li class="todo"><div class="t"><span class="tid">T3.3</span><span class="tt">第 2 轮验证</span><span class="tag idle">待办</span></div></li>
 <li class="todo"><div class="t"><span class="tid">T3.4</span><span class="tt">收敛判定（难度曲线单调、stuck 达标）</span><span class="tag idle">待办</span></div></li>
   </ul>
@@ -204,7 +204,7 @@ footer{margin-top:56px;padding-top:20px;border-top:1px solid var(--rule);color:v
 <div class="scroll"><table>
 <thead><tr><th>批次</th><th class="n">关数</th><th class="n">difficulty</th><th class="n">stuck</th><th class="n">盲转/关</th><th class="n">多转/关</th></tr></thead>
 <tbody>
-<tr><td>R1 · grok xhigh</td><td class="n">39</td><td class="n">2.05</td><td class="n">1.36</td><td class="n">0.15</td><td class="n">0.18</td></tr>
+<tr><td>R1 · grok xhigh</td><td class="n">49</td><td class="n">2.06</td><td class="n">1.41</td><td class="n">0.16</td><td class="n">0.31</td></tr>
 <tr><td>Codex CLI · gpt-6-astra low</td><td class="n">18</td><td class="n">2.44</td><td class="n">1.44</td><td class="n">1.17</td><td class="n">1.22</td></tr>
 <tr><td>Codex CLI · spark xhigh</td><td class="n">18</td><td class="n">3.11</td><td class="n">2.28</td><td class="n">1.17</td><td class="n">1.17</td></tr>
 <tr><td>Grok Build CLI · xhigh</td><td class="n">18</td><td class="n">2.39</td><td class="n">1.83</td><td class="n">1.17</td><td class="n">1.22</td></tr>
@@ -219,6 +219,7 @@ footer{margin-top:56px;padding-top:20px;border-top:1px solid var(--rule);color:v
 
 <h2><span class="num">F</span>日志</h2>
 <ul class="log">
+<li><b>R2 依据</b>后段 14 条抱怨里两类：路线太长（感知，已对照 v0.5 基线否掉）与「转了没反应」（机械，可设闸门）。只改后者：endgameMinOpen 2→3、doubleDead 无闸门→≤2。两条合计只留 16% 候选，所以先扩池</li>
 <li><b>未擅自改动</b>agent 33 条抱怨里两大主题是路线太长（68 格 27 弯）与紧贴易看漏。但已上线的 v0.5 在这两项上更严重（最长 88 格 vs 84 格），属于游戏本来的性格；且文字盘面会同时夸大和缩小感知问题。因此只在审核页标出，不擅自设闸门</li>
 <li><b>R1 结论</b>难度评分在这批关卡上无区分度（26/27 都是 2 分），原因是文字 bench 把判断白送给了 agent。结论：agent 轮次用于抓缺陷（死局、盲转、空点、演出），难度排序只能靠机械假设 + 人工审核。这条改变了后续流程的设计</li>
 <li><b>演出</b>离场动画封顶定稿（拐点 2.4s / 上限 3.2s），最长 17.4s→3.5s；拐点以下手感不变。同时发现开局演出是结构性缺陷并在构造里修掉</li>