feat(统计): 流程图统计列出「最常见的错」，不再显示新评法下没意义的平均分

新评法（走例子）没有四项分、几乎没有评语，雷达图、各项平均分、词云都拼不出来，
页面上只剩一个等级圆环。改成：
- 「最常见的错」：每张图第一组没走对的原因原样数一下（「『一级果』多输出了一行
  『一级果』2 张」），最多 8 条；全是新数据时放在等级分布旁边，新老混着时顶替词云
- 只有新数据时「每人最好的一次」铺满一行、分几栏
- 去掉「平均分」：新评法的分数只是走对的比例，看它不如看「拿到 A / S」；
  「每人最好的一次」也只写等级
老数据（2026-10 之前）照旧是四项分和词云。

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

apps/api/src/routes/flowchart.ts

@@ -610,6 +610,7 @@ flowchartRoutes.get("/flowcharts/statistics", requireTeacher, async (c) => {
       personCount: roster.length,
       completedCount: 0,
       wordFrequencies: [],
+      commonMistakes: [],
       // 一条提交都没有时，花名册上的人**全都**是「没做」—— 原来这里写死空数组，
       // 于是一节课刚开始、最该点名的时候，教师面板反而一个名字都不给
       dataUnaccepted: roster.map((row) => ({
@@ -645,8 +646,16 @@ flowchartRoutes.get("/flowcharts/statistics", requireTeacher, async (c) => {
   const pushText = (value: string) => {
     if (texts.length < WORDCLOUD_TEXT_LIMIT) texts.push(value)
   }
+  const mistakes = new Map<string, number>()
   for (const row of textRows) {
-    for (const [key, value] of Object.entries(asRecord(row.criteria))) {
+    const report = asRecord(row.criteria)
+    if (report.version === 2 && Array.isArray(report.cases)) {
+      const first = report.cases.map((item) => asRecord(item)).find((item) => item.ok === false)
+      if (typeof first?.why === "string" && first.why) {
+        mistakes.set(first.why, (mistakes.get(first.why) ?? 0) + 1)
+      }
+    }
+    for (const [key, value] of Object.entries(report)) {
       const detail = asRecord(value)
       // 和上面那条聚合同一道闸：分数不是数字的项当没配过，满分和评语也都不收
       if (typeof detail.score !== "number") continue
@@ -676,6 +685,10 @@ flowchartRoutes.get("/flowcharts/statistics", requireTeacher, async (c) => {
     personCount: roster.length,
     completedCount: totals.completedCount,
     wordFrequencies: await buildWordFrequencies(texts),
+    commonMistakes: [...mistakes]
+      .sort((a, b) => b[1] - a[1])
+      .slice(0, 8)
+      .map(([text, n]) => ({ text, count: n })),
     dataUnaccepted: roster
       .filter((row) => !submitted.has(row.id))
       .map((row) => ({

apps/web/src/oj/statistics/components/FlowStats.vue

@@ -200,13 +200,11 @@ const people = computed(() => [
   ...props.data.dataUnaccepted.map((row) => ({
     username: row.username,
     grade: null as string | null,
-    score: null as number | null,
     count: 0,
   })),
   ...props.data.people.map((row) => ({
     username: row.username,
     grade: row.bestGrade,
-    score: row.bestScore,
     count: row.count,
   })),
 ])
@@ -229,7 +227,6 @@ function gradeStyle(grade: string | null) {
   <div class="flow-stats">
     <div class="summary">
       <StatItem label="提交" :value="data.totalCount" unit="张" />
-      <StatItem label="平均分" :value="data.avgScore" />
       <StatItem
         label="拿到 A / S"
         :value="`${goodCount} / ${personCount}`"
@@ -267,31 +264,54 @@ function gradeStyle(grade: string | null) {
             <Doughnut :key="chartKey" :data="gradeData" :options="gradeOptions" />
           </div>
         </div>
-        <div v-if="criteria.length" class="card radar">
-          <div class="card-title">四项评分（平均得分率）</div>
-          <div class="chart">
-            <Radar :key="chartKey" :data="radarData" :options="radarOptions" />
+        <template v-if="criteria.length">
+          <div class="card radar">
+            <div class="card-title">四项评分（平均得分率）</div>
+            <div class="chart">
+              <Radar :key="chartKey" :data="radarData" :options="radarOptions" />
+            </div>
           </div>
-        </div>
-        <div v-if="criteria.length" class="card grow">
-          <div class="card-title">各项平均分</div>
-          <div class="chart"><Bar :key="chartKey" :data="barData" :options="barOptions" /></div>
+          <div class="card grow">
+            <div class="card-title">各项平均分</div>
+            <div class="chart"><Bar :key="chartKey" :data="barData" :options="barOptions" /></div>
+          </div>
+        </template>
+        <!-- 全是 2026-10 之后「走例子」评的图：没有四项分，这个位置给最常见的错 -->
+        <div v-else class="card grow">
+          <div class="card-title">最常见的错（最近交的图里）</div>
+          <ol v-if="data.commonMistakes.length" class="mistakes">
+            <li v-for="item in data.commonMistakes" :key="item.text">
+              <span class="mistake-text">{{ item.text }}</span>
+              <span class="muted">{{ item.count }} 张</span>
+            </li>
+          </ol>
+          <div v-else class="muted">交上来的图都走对了</div>
         </div>
       </div>
       <div class="row-cards bottom">
-        <div class="card grow">
+        <!-- 新老评法混着：有走例子的错就列错，只有老数据时照旧是词云 -->
+        <div v-if="criteria.length && data.commonMistakes.length" class="card grow">
+          <div class="card-title">最常见的错（最近交的图里）</div>
+          <ol class="mistakes">
+            <li v-for="item in data.commonMistakes" :key="item.text">
+              <span class="mistake-text">{{ item.text }}</span>
+              <span class="muted">{{ item.count }} 张</span>
+            </li>
+          </ol>
+        </div>
+        <div v-else-if="criteria.length" class="card grow">
           <div class="card-title">常见问题高频词（最近的评语里）</div>
           <div class="cloud"><canvas ref="cloudCanvas"></canvas></div>
           <div v-if="!data.wordFrequencies.length" class="muted">评语太少，还拼不出词云</div>
         </div>
-        <div class="card people">
+        <div class="card people" :class="{ wide: !criteria.length }">
           <div class="card-title">每人最好的一次（没交的在前）</div>
           <div v-if="data.peopleTruncated" class="muted">人太多，只列了成绩靠后的 500 位</div>
           <div class="people-list">
             <div v-for="row in people" :key="row.username" class="person">
               <UserName :username="row.username" class="p-name" />
               <span class="grade-pill" :style="gradeStyle(row.grade)">
-                {{ row.grade ? `${row.grade} 级 ${row.score ?? 0} 分` : "没交" }}
+                {{ row.grade ? `${row.grade} 级` : "没交" }}
               </span>
               <span class="muted">{{ row.count }} 次</span>
             </div>
@@ -489,4 +509,35 @@ function gradeStyle(grade: string | null) {
     max-height: 360px;
   }
 }
+
+.mistakes {
+  margin: 0;
+  padding-left: 20px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  font-size: 14px;
+  line-height: 1.6;
+}
+
+.mistakes li {
+  padding-left: 2px;
+}
+
+.mistake-text {
+  margin-right: 8px;
+}
+
+/* 没有词云、四项分的时候，每人一格铺满一行 */
+.card.people.wide {
+  flex: 1 1 0;
+  width: auto;
+}
+
+.card.people.wide .people-list {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
+  align-content: start;
+  column-gap: 24px;
+}
 </style>

packages/contract/src/flowchart.ts

@@ -97,6 +97,12 @@ export const flowchartStatisticsSchema = z.object({
   personCount: z.number().int(),
   completedCount: z.number().int(),
   wordFrequencies: z.array(z.object({ word: z.string(), count: z.number().int() })),
+  /**
+   * 2026-10 起「走例子」评的图里最常见的错：每张图取第一组没走对的原因（「『一级果』多输出了
+   * 一行『一级果』」），同一句话数一下，最多 8 条。新评法几乎没有评语，词云拼不出来，
+   * 而同一个错在一个班里往往原样出现几十次 —— 老师要看的就是它
+   */
+  commonMistakes: z.array(z.object({ text: z.string(), count: z.number().int() })),
   // 与提交统计共用「未完成学生」的形状，见 submission.ts 的 unacceptedStudentSchema
   dataUnaccepted: z.array(z.object({ username: z.string(), realName: z.string() })),
   /**