fix: 修复聊天预览滚动抽搐与键盘事件类型

任务: 解决问答预览页滚动抽搐并补齐类型检查报错\n\n- 在 chat 组件中改为自定义回到底部按钮，避免内置按钮导致滚动抖动\n- 统一收口流式结束状态，结束时关闭 typing/loading\n- 修复 FaqEditDialog 的 keydown 参数类型，兼容 Event | KeyboardEvent

easyflow-ui-admin/app/src/views/ai/documentCollection/FaqEditDialog.vue

@@ -101,8 +101,12 @@ const focusAnswerEditor = () => {
   });
 };
 
-const handleQuestionKeydown = (event: KeyboardEvent) => {
-  if (event.key === 'Tab' && !event.shiftKey) {
+const handleQuestionKeydown = (event: Event | KeyboardEvent) => {
+  if (
+    event instanceof KeyboardEvent &&
+    event.key === 'Tab' &&
+    !event.shiftKey
+  ) {
     event.preventDefault();
     focusAnswerEditor();
   }