chore：导航栏删除在线客服

pages_tool/ai-chat/index.vue

@@ -7,16 +7,6 @@
           <text class="iconfont icon-back"></text>
         </button>
         <!-- 占位元素，确保布局平衡 -->
-        <view v-show="!showBackButton" class="placeholder"></view>
-      </view>
-      <view class="header-center">
-        <text class="header-subtitle">在线为您服务</text>
-      </view>
-      <view class="header-right">
-        <button class="menu-btn" v-show="showMenuButton" @click="showMenu">
-          <text>⚙️</text>
-        </button>
-        <!-- 占位元素，确保布局平衡 -->
         <view v-show="!showMenuButton" class="placeholder"></view>
       </view>
     </view>