修复 H5 嵌入小程序导航栏冲突

- 识别微信小程序 web-view 宿主环境
- 宿主导航存在时隐藏 H5 自绘返回与页面标题
- 收回详情、搜索、讲解列表页面顶部预留空间

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/pages/exhibit/detail.vue

@@ -20,7 +20,7 @@
             mode="aspectFill"
           />
           <view class="hero-image-shade"></view>
-          <view class="hero-back" @tap.stop="handleBack">
+          <view v-if="!shouldUseHostNavigation" class="hero-back" @tap.stop="handleBack">
             <text class="hero-back-icon">‹</text>
           </view>
           <view class="hero-copy">
@@ -128,6 +128,7 @@ import {
 import {
   EXPLAIN_DETAIL_PLACEHOLDER_IMAGE
 } from '@/utils/placeholders'
+import { isEmbeddedInWechatMiniProgram } from '@/utils/hostEnvironment'
 
 const defaultDetail: ExplainDetailPageViewModel = {
   id: '',
@@ -170,6 +171,7 @@ const detailTextLoadedByLanguage = ref<Record<AudioLanguage, boolean>>({
 })
 // 讲解详情页位置入口暂未开放，避免误导用户进入位置预览流程。
 const isLocationActionVisible = false
+const shouldUseHostNavigation = computed(() => isEmbeddedInWechatMiniProgram())
 
 const contentLanguageOptions: Array<{
   value: AudioLanguage
@@ -208,7 +210,6 @@ const currentAudioTarget = computed(() => ({
   lang: selectedAudioLanguage.value
 }))
 const isCurrentDetailAudio = computed(() => globalAudioPlayer.isCurrentSource(currentAudioTarget.value))
-
 const isCurrentDetailAudioTarget = computed(() => {
   const source = globalAudioPlayer.currentSource.value
   const targetType = exhibit.value.audio.playTargetType || 'ITEM'
@@ -699,7 +700,7 @@ const handleBack = () => {
 
 .content {
   height: 100%;
-  padding: 84px 20px calc(104px + env(safe-area-inset-bottom));
+  padding: var(--guide-page-detail-top-padding, 84px) 20px calc(104px + env(safe-area-inset-bottom));
   box-sizing: border-box;
 }
 
@@ -967,7 +968,6 @@ const handleBack = () => {
   background: rgba(249, 250, 251, 0.96);
 }
 
-
 .location-btn {
   height: 52px;
   display: flex;