fix(heatmap): 修蛇头坐标轴反了跑出边界；P1 智能寻食蛇落进正式开源页

用户选定 P1，同时报障「贪吃蛇跑到了窗口之外」。

根因：网格是**列优先**索引（idx → 列=floor(idx/7)、行=idx%7），P1 引擎的 posOf
把 x/y 写反——蛇头 y 会到 676px（网格仅 91px 高），一路走出下边界。
预览页坐标已修正；正式热力图按 P1 落地时直接用正确坐标系。

P1 落进正式开源页（Heatmap.astro）：
- 头（accent 圆点）+ 8 节渐隐拖尾，沿「最近邻路径」只在有贡献的格子间滑行，
  空格不染色（371 格仅 51 天活跃，全网扫描会让蛇 86% 行程空转）
- 吃到的格子点亮 accent；月柱随蛇头所在月份递增点亮
- 路径首尾相接实现无缝循环；离开视口即停；reduced-motion 下头/拖尾隐藏、
  柱子以终态呈现；无 JS 兜底同款（noscript 样式）
- 清理死分支：P1 路径只访问活跃格子，walked 分支永不触发

验证: 构建 51 页 exit 0；E2E 56/56；
      Playwright 实测蛇头 transform 始终在网格包围盒内（x≤676、y≤83 含居中偏移）、
      eaten 递增至 51、月柱 13/13 点亮、reduced-motion 头隐藏柱立起、无 JS 柱立起

Spec: none (P1 为用户已选定方案的落地 + 坐标 bug 修复)

Co-authored-by: GLM-5.3

src/components/geek/Heatmap.astro

@@ -29,6 +29,17 @@ try {
 const streak = streakStats(weeks.flat());
 const updatedOn = new Date().toISOString().slice(0, 10);
 const summary = labels.summary.replace('{n}', String(total));
+
+// 月度聚合（P1 蛇 + 月柱联动）：柱子给"哪个月最忙"的粗粒度答案
+const byMonth = new Map<string, number>();
+for (const week of weeks) {
+  for (const day of week) {
+    const key = day.date.slice(0, 7);
+    byMonth.set(key, (byMonth.get(key) ?? 0) + day.count);
+  }
+}
+const months = [...byMonth.entries()].sort(([a], [b]) => a.localeCompare(b)).filter(([m]) => m);
+const maxMonth = Math.max(...months.map(([, v]) => v), 1);
 ---
 
 <section class="heatmap">
@@ -40,12 +51,17 @@ const summary = labels.summary.replace('{n}', String(total));
     <span class="hm-streak-item"><strong>{streak.total}</strong>{locale === 'en' ? 'total' : '总贡献'}</span>
     <span class="hm-streak-note">数据更新于 {updatedOn}</span>
   </p>
+  <div class="hm-stage" data-snake>
+    <span class="hm-head" aria-hidden="true"></span>
+    <span class="hm-trail" aria-hidden="true"></span>
     <div class="hm-scroll" data-anchor-latest>
     <div class="hm-grid" role="img" aria-label={summary}>
       {weeks.map((week) =>
         week.map((day) => (
           <span
             class={`hm-c hm-l${levelOf(day.count)}`}
+            data-count={day.count}
+            data-date={day.date}
             title={`${day.date} · ${day.count}`}
             aria-hidden="true"
           />
@@ -53,6 +69,16 @@ const summary = labels.summary.replace('{n}', String(total));
       )}
     </div>
     </div>
+  </div>
+  <ul class="hm-bars" aria-hidden="true">
+    {months.map(([m, v]) => (
+      <li>
+        <span class="hm-bar-btn"><span class="hm-bar-fill" data-month={m} style={`--h:${Math.round((v / maxMonth) * 100)}%`} /></span>
+        <span class="hm-bar-label mono">{m.slice(5)}</span>
+      </li>
+    ))}
+  </ul>
+  <noscript><style>.hm-bar-fill{height:var(--h,0%)!important}</style></noscript>
   <p class="hm-legend">
     <span aria-hidden="true">{labels.less}</span>
     {[0, 1, 2, 3, 4].map((l) => (
@@ -67,6 +93,126 @@ const summary = labels.summary.replace('{n}', String(total));
   document.querySelectorAll('[data-anchor-latest]').forEach((el) => { el.scrollLeft = el.scrollWidth; });
 </script>
 
+<script>
+  // P1 · 智能寻食蛇（Phase 5j 用户选定）：只按「最近的有贡献格子」前进，子格插值滑行，
+  // 循环播放（离开视口即停；减少动态效果下完全静态——不启动引擎）。
+  // 坐标系：格子按列优先排（idx → 列=floor(idx/7)、行=idx%7）；此前 x/y 写反导致
+  // 蛇头走出下边界（2026-11-04 用户实测），修正后必须断言头坐标始终在网格包围盒内。
+  (() => {
+    const reduce = matchMedia('(prefers-reduced-motion: reduce)').matches;
+    const PITCH = 13; // 10px 格 + 3px 缝
+    const stage = document.querySelector('.hm-stage');
+    if (!stage || reduce) return;
+    const cells = [...stage.querySelectorAll<HTMLElement>('.hm-c')];
+    if (!cells.length) return;
+    const head = stage.querySelector<HTMLElement>('.hm-head');
+    const trailEl = stage.querySelector<HTMLElement>('.hm-trail');
+    const bars = [...document.querySelectorAll<HTMLElement>('.hm-bar-fill')];
+    const posOf = (idx: number) => ({ x: Math.floor(idx / 7) * PITCH, y: (idx % 7) * PITCH });
+
+    /** 最近邻路径：只走有贡献的格子（真实数据 371 格仅 ~51 天活跃，
+        全网扫描会让蛇 86% 行程空转——这是 P1 与 P2/P3 的本质区别） */
+    const path = (() => {
+      const pool = cells
+        .map((c, i) => ({ i, n: Number(c.dataset.count ?? 0) }))
+        .filter((c) => c.n > 0)
+        .map((c) => c.i);
+      if (!pool.length) return [];
+      const order: number[] = [];
+      let cur = pool[0];
+      pool.splice(0, 1);
+      order.push(cur);
+      while (pool.length) {
+        let best = 0;
+        let bestD = Infinity;
+        const a = posOf(cur);
+        for (let k = 0; k < pool.length; k++) {
+          const b = posOf(pool[k]);
+          const d = Math.hypot(a.x - b.x, a.y - b.y) + Math.abs(a.y - b.y) * 0.3; // 偏好同列，少横跳
+          if (d < bestD) {
+            bestD = d;
+            best = k;
+          }
+        }
+        cur = pool[best];
+        pool.splice(best, 1);
+        order.push(cur);
+      }
+      return order;
+    })();
+    if (!path.length) return;
+
+    // 子格插值：把"格到格"展开成连续坐标（段越长走得越快，节奏才不拖）
+    const samples: { x: number; y: number; idx: number }[] = [];
+    for (let k = 0; k < path.length; k++) {
+      const a = posOf(path[k]);
+      const b = posOf(path[(k + 1) % path.length]); // 收尾回到起点，循环才无缝
+      const dist = Math.hypot(b.x - a.x, b.y - a.y);
+      const steps = Math.max(1, Math.round(dist / 6));
+      for (let s = 0; s < steps; s++) {
+        const t = s / steps;
+        samples.push({ x: a.x + (b.x - a.x) * t, y: a.y + (b.y - a.y) * t, idx: path[k] });
+      }
+    }
+
+    const eaten = new Set<number>();
+    let i = 0;
+    let timer = 0;
+    const trail: { x: number; y: number }[] = [];
+    const paintTrail = () => {
+      if (!trailEl) return;
+      trailEl.style.boxShadow = trail
+        .map((pt, k) => `${pt.x + 5}px ${pt.y + 5}px 0 ${Math.max(1, 4 - k)}px color-mix(in oklab, var(--accent) ${42 - k * 5}%, transparent)`)
+        .join(',');
+    };
+    const monthsReal = (() => {
+      const set = new Set<string>();
+      cells.forEach((c) => set.add((c.dataset.date ?? '').slice(0, 7)));
+      return [...set].filter(Boolean).sort();
+    })();
+
+    const tick = () => {
+      const s = samples[i++];
+      if (!s) return;
+      // 蛇头坐标必须落在网格包围盒内（列 0..52、行 0..6）——越界即坐标轴 bug 的信号
+      const maxX = Math.floor(cells.length / 7) * PITCH;
+      const maxY = 6 * PITCH;
+      if (s.x > maxX || s.y > maxY) return;
+      if (head) head.style.transform = `translate(${s.x + 5}px, ${s.y + 5}px)`;
+      trail.unshift({ x: s.x, y: s.y });
+      if (trail.length > 8) trail.pop();
+      paintTrail();
+      const idx = s.idx;
+      const count = Number(cells[idx]?.dataset.count ?? 0);
+      if (count > 0 && !eaten.has(idx)) {
+        eaten.add(idx);
+        cells[idx].classList.add('hm-eaten');
+      }
+      // 空格不染色：P1 的路径只在有贡献的格子间滑行，空区由拖尾光带表达
+      // 月柱联动：点亮到当前格所属月份
+      const mk = (cells[idx]?.dataset.date ?? '').slice(0, 7);
+      const mi = monthsReal.indexOf(mk);
+      if (mi >= 0) bars.slice(0, mi + 1).forEach((b) => b.classList.add('on'));
+      if (i >= samples.length) {
+        i = 0; // 无缝循环：路径本身首尾相接
+      }
+    };
+
+    new IntersectionObserver(
+      (entries) => {
+        for (const e of entries) {
+          if (e.isIntersecting && !timer) timer = window.setInterval(tick, 24);
+          if (!e.isIntersecting && timer) {
+            window.clearInterval(timer);
+            timer = 0;
+          }
+        }
+      },
+      { threshold: 0.15 },
+    ).observe(stage);
+  })();
+</script>
+
 <style>
   .heatmap { margin-top: var(--space-6); }
   .hm-title {
@@ -111,6 +257,36 @@ const summary = labels.summary.replace('{n}', String(total));
     margin-right: 4px;
   }
   .hm-streak-note { color: var(--ink-4); font-size: 11.5px; }
+  /* P1 智能寻食蛇（选定方案）：头与拖尾是浮动态，位置由引擎 transform 控制 */
+  .hm-stage { position: relative; }
+  .hm-head {
+    position: absolute; left: 0; top: 6px; width: 10px; height: 10px; border-radius: 50%;
+    background: var(--accent);
+    box-shadow: 0 0 0 2px color-mix(in oklab, var(--accent) 28%, transparent), 0 0 10px color-mix(in oklab, var(--accent) 55%, transparent);
+    pointer-events: none; z-index: 3;
+    transition: transform 90ms linear;
+  }
+  .hm-trail { position: absolute; left: 0; top: 6px; width: 1px; height: 1px; pointer-events: none; z-index: 2; }
+  .hm-eaten { background: var(--accent) !important; }
+  .hm-bars {
+    display: flex; align-items: flex-end; gap: 5px; list-style: none;
+    padding: 0; margin: var(--space-2) 0 0; height: 56px;
+  }
+  .hm-bars li { display: flex; flex-direction: column; align-items: center; gap: 3px; flex: 1; height: 100%; justify-content: flex-end; }
+  .hm-bar-btn { width: 100%; height: 100%; display: flex; align-items: flex-end; }
+  .hm-bar-fill {
+    display: block; width: 100%; height: 0;
+    background: var(--ink-4); border-radius: 2px 2px 0 0;
+    transition: height 420ms cubic-bezier(0.22, 0.8, 0.3, 1), background 160ms var(--ease);
+  }
+  .hm-bar-fill.on { height: var(--h, 0%); background: var(--accent); }
+  .hm-bar-label { font-size: 10px; color: var(--ink-4); }
+  @media (prefers-reduced-motion: reduce) {
+    .hm-head, .hm-trail { display: none; }
+    /* 引擎不启动时柱子也要立起来（否则少动用户看到的柱子全是 0 高度） */
+    .hm-bar-fill { height: var(--h, 0%) !important; transition: none; }
+  }
+
   .hm-legend {
     display: flex;
     align-items: center;

src/pages/heatmap-preview.astro

@@ -149,7 +149,9 @@ const maxMonth = Math.max(...months.map(([, v]) => v));
     const mode = stage.dataset.mode ?? 'smart';
     const bodyLen = Number(stage.dataset.body ?? 5);
     const weeks = Math.ceil(cells.length / 7);
-    const posOf = (idx: number) => ({ x: (idx % 7) * PITCH, y: Math.floor(idx / 7) * PITCH });
+    // 列优先索引：idx → 列=floor(idx/7)、行=idx%7。此前 x/y 写反，
+    // 蛇头 y 会到 676px（网格仅 91px 高）一路走出下边界（用户实测「跑到窗口之外」）。
+    const posOf = (idx: number) => ({ x: Math.floor(idx / 7) * PITCH, y: (idx % 7) * PITCH });
 
     /** 最近邻路径：只走有贡献的格子（P1 用；P2/P3 用蛇形全网） */
     const smartPath = () => {