fix(growth): rank the rate board by a smoothed score

Show the real percentage on the card, but sort with delta / (baseline + prior) so a small baseline cannot dominate. Same-day publishes stay off the rate board.

reaction_board/web/static/views/about.js

@@ -50,6 +50,7 @@ export async function renderAbout(root) {
         <li><strong>播放 / 投币 / 收藏 / 评论</strong>：直接取当日快照；弹幕与转发不单列，已并入“互动”。</li>
         <li><strong>互动</strong>：点赞 + 投币 + 收藏。综合热度也使用全部七项指标，按配置权重加权。</li>
         <li><strong>互动率</strong>：(点赞 + 投币 + 收藏) / 播放；播放不足 100 不计算。</li>
+        <li><strong>播放增速</strong>：卡片上的百分比是增量 / 基线播放。排序用增量 / (基线 + ${analytics.growth_rate_prior})，避免小基数霸榜。当日发布没有基线，不进增速榜。</li>
         <li><strong>综合热度</strong>：每项先 <code>log1p</code>，再按中位数与 IQR 做稳健标准化，最后加权求和。分数只用于同一批数据内排序，不能跨日期比较。</li>
         <li><strong>内容效率</strong>：播放 / 内容小时。内容小时 = 视频总时长（多 P 为各 P 之和）÷ 3600。榜单里的单条视频用收缩后的估计：<code>(播放 + κ·μ₀) / (小时 + κ)</code>，κ 默认 ${analytics.video_shrink_minutes} 分钟、μ₀ 为全库播放/小时；详情页保留原始播放/小时。</li>
         <li><strong>互动效率</strong>：互动 / 内容小时，互动口径与收缩方式同上。</li>

reaction_board/web/static/views/rankings.js

@@ -166,6 +166,7 @@ function listHtml(data, scope, sort, startRank) {
     return videoCard(item, {
       rank: startRank + index, primary: primary.primary,
       primaryLabel: primary.label, primaryText: primary.text,
+      growthField: sort === "growth_rate" ? "rate" : "delta",
     });
   }).join("")}</div>`;
 }
@@ -179,9 +180,18 @@ function durationNote(data) {
   return `<div class="section-note">内容效率与互动效率：时长 ≥ ${filter.min_duration_seconds} 秒、发布满 ${filter.maturity_days} 天、播放 ≥ ${filter.min_view}${shrink}；时长缺失不参与。</div>`;
 }
 
-function growthNote(sort, growthDays) {
-  if (sort !== "growth" && sort !== "growth_rate") return "";
-  if (Number(growthDays) !== 1) return "";
+function growthNote(sort, growthDays, prior) {
+  if (sort === "growth_rate") {
+    const strength = Number(prior);
+    const smooth = Number.isFinite(strength)
+      ? `百分比是真实相对增量；排序按平滑增速（基线 + ${strength}）。`
+      : "百分比是真实相对增量；排序按平滑增速。";
+    const cold = Number(growthDays) === 1
+      ? "当日发布不进增速榜。更早发布的新入库按入库时播放量起算，需要当天至少两次采样。"
+      : "";
+    return `<div class="section-note">${smooth}${cold}</div>`;
+  }
+  if (sort !== "growth" || Number(growthDays) !== 1) return "";
   return `<div class="section-note">近 1 日：当日发布按 0 起算；更早发布的新入库按入库时播放量起算，需要当天至少两次采样。</div>`;
 }
 
@@ -251,7 +261,7 @@ async function renderScope(root, { query }, scope) {
     </header>
     ${controls({ scope, sort, within, year, growthDays, q, years })}
     ${durationNote(data)}
-    ${growthNote(sort, growthDays)}
+    ${growthNote(sort, growthDays, data.growth_rate_prior)}
     ${data.available === false ? `<div class="notice-row warning">
       <strong>${sort.startsWith("growth") ? "增长数据尚不可用" : "榜单筛选后为空"}</strong>
       <span>${escapeHtml(data.reason || "")}</span>