feat(StudyDetailPage): 添加默认展示区并引入VanDivider组件

在StudyDetailPage.vue中添加默认展示区，用于显示课程标题，并更新components.d.ts以引入VanDivider组件

@@ -34,6 +34,7 @@ declare module 'vue' {
     VanCheckbox: typeof import('vant/es')['Checkbox']
     VanDatePicker: typeof import('vant/es')['DatePicker']
     VanDialog: typeof import('vant/es')['Dialog']
+    VanDivider: typeof import('vant/es')['Divider']
     VanEmpty: typeof import('vant/es')['Empty']
     VanField: typeof import('vant/es')['Field']
     VanForm: typeof import('vant/es')['Form']

 <!--
   * @Date: 2025-04-07
   * @Description: 学习详情页面
- -->
+-->
 <template>
     <div class="study-detail-page bg-gradient-to-b from-green-50/70 to-white/90 min-h-screen pb-20">
         <div v-if="course" class="flex flex-col h-screen">
@@ -64,6 +64,13 @@
                         </div>
                     </div>
                 </div>
+
+                <!-- 默认展示区 -->
+                <div v-else class="relative" style="border-bottom: 1px solid #e5e7eb;">
+                    <div class="h-24 bg-white flex items-center justify-center px-4">
+                        <h3 class="text-lg font-medium text-gray-900 truncate">{{ course.title }}</h3>
+                    </div>
+                </div>
                 <!-- 标签页区域 -->
                 <div class="px-4 py-3 bg-white">
                     <van-tabs v-model:active="activeTab" sticky animated swipeable shrink @change="handleTabChange">