feat: add tab navigation utility for keyboard accessibility

.vitepress/theme/utils/tabNavigation.ts

@@ -0,0 +1,37 @@
+/**
+ * 处理容器内的 Tab 键导航
+ * @param container 包含可聚焦元素的容器，规定选择范围
+ * @param items 容器内的可聚焦元素列表
+ * @param isShiftKey 是否按下了 Shift 键（用于反向导航）
+ * @param isESCKey 是否按下了 Esc 键（用于取消内容焦点）
+ */
+export const handleTabNavigation = (
+  container: HTMLElement | null,
+  items: NodeListOf<Element> | null,
+  isShiftKey?: boolean,
+  isESCKey?: boolean
+): void => {
+  if (!container || !items || items.length === 0) return;
+
+  const currentFocused = document.activeElement as HTMLElement;
+  const itemsArray = Array.from(items) as HTMLElement[];
+
+  // 检查当前焦点是否在容器范围内
+  const isInContainer = container.contains(currentFocused);
+  const currentIndex = isInContainer ? itemsArray.indexOf(currentFocused) : -1;
+
+  if (isShiftKey) {
+    // Shift + Tab: 反向切换
+    const nextIndex = currentIndex <= 0 ? itemsArray.length - 1 : currentIndex - 1;
+    itemsArray[nextIndex].focus();
+  } else {
+    // Tab: 正向切换
+    const nextIndex = currentIndex < itemsArray.length - 1 ? currentIndex + 1 : 0;
+    itemsArray[nextIndex].focus();
+  }
+
+  // 取消焦点
+  if (isESCKey) {
+    currentFocused.blur();
+  }
+};