feat: 碎片列表增加序号标识

- StartTask.vue 碎片列表前显示圆形序号
- ReviewDetail.vue 残片标签改为「残片1」「残片2」等带序号形式

src/components/ReviewDetail.vue

@@ -243,13 +243,13 @@ onMounted(() => {
 
         <div class="session-fragments" v-if="session.fragments.length > 0">
           <span
-            v-for="f in session.fragments"
+            v-for="(f, idx) in session.fragments"
             :key="f.id"
             class="clickable-text"
             :class="{ active: contentType === 'fragment' && f.id === contentId }"
             @click="goToDetail('fragment', f.id)"
           >
-            <span class="label-tag fragment-tag">残片</span>
+            <span class="label-tag fragment-tag">残片{{ idx + 1 }}</span>
             {{ f.content.length > 150 ? f.content.substring(0, 150) + "..." : f.content }}
           </span>
         </div>

src/components/StartTask.vue

@@ -370,10 +370,11 @@ onUnmounted(() => {
     <article class="surface-card fragments-card" v-if="fragmentsList.length > 0">
       <h3>当前会话学习残片</h3>
       <div
-        v-for="fragment in fragmentsList"
+        v-for="(fragment, index) in fragmentsList"
         :key="fragment.id"
         class="fragment-item"
       >
+        <span class="fragment-index">{{ index + 1 }}</span>
         <template v-if="editingFragmentId === fragment.id">
           <el-input
             v-model="editFragmentContent"
@@ -541,6 +542,20 @@ onUnmounted(() => {
   border-bottom: none;
 }
 
+.fragment-index {
+  flex-shrink: 0;
+  width: 24px;
+  height: 24px;
+  border-radius: 50%;
+  background: var(--green-600);
+  color: #fff;
+  font-size: 12px;
+  font-weight: 700;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
 .fragment-content {
   flex: 1;
   font-size: 14px;