fix(ai-assistant): Modal 模式移动端恢复居中弹框，不再沉浸全屏

移动端仅聊天(chat)浮窗保留全屏沉浸，Modal 模式两端统一为居中模态，
回退 f6067d1bd 对 Modal 的移动端全屏处理；删除随之失效的
.ai-assistant-modal .is-mobile-fullscreen 样式块。

resources/assets/js/components/AIAssistant/index.vue

@@ -3475,31 +3475,6 @@ export default {
             max-height: calc(var(--window-height) - var(--status-bar-height) - var(--navigation-bar-height) - 136px);
         }
     }
-
-    // 移动端 fullscreen Modal:参考全局搜索,顶部留 status-bar + 46px,顶部圆角
-    &.is-mobile-fullscreen {
-        .ivu-modal-content {
-            margin-top: calc(var(--status-bar-height, 0px) + 46px);
-            margin-bottom: 0;
-            border-top-left-radius: 18px !important;
-            border-top-right-radius: 18px !important;
-        }
-        .ivu-modal-body {
-            display: flex;
-            flex-direction: column;
-        }
-        .ai-assistant-header {
-            margin-right: 24px;
-        }
-        .ai-assistant-content {
-            flex: 1;
-            min-height: 0;
-            max-height: none;
-        }
-        .ai-assistant-input {
-            padding-bottom: calc(12px + var(--navigation-bar-height, 0px));
-        }
-    }
 }
 
 body.window-portrait {

resources/assets/js/components/AIAssistant/modal.vue

@@ -58,10 +58,9 @@
         v-else
         v-model="visible"
         :width="shouldCreateNewSession ? '440px' : '600px'"
-        :fullscreen="isMobile"
         :mask-closable="false"
         :footer-hide="true"
-        :class-name="isMobile ? 'ai-assistant-modal is-mobile-fullscreen' : 'ai-assistant-modal'">
+        class-name="ai-assistant-modal">
         <template #header>
             <slot name="header"></slot>
         </template>