feat(NavBar): try to fix bar not display

.vitepress/theme/components/NavBar.vue

@@ -14,6 +14,20 @@ const navSegment = computed(() => {
   return Array.isArray(items) && items.length > 0 ? items : [];
 });
 
+/**
+ * 计算导航栏模式 (Rail / Bar)
+ */
+const navMode = computed(() => {
+  const currentWidth = screenWidthStore.screenWidth;
+  const breakpoint = screenWidthStore.breakpoint;
+
+  if (currentWidth <= 840) {
+    return "bar";
+  }
+
+  return currentWidth > breakpoint ? "rail" : "bar";
+});
+
 // 规范化路径
 function normalizePath(path: string): string {
   return path.replace(/(\/index)?\.(md|html)$/, "").replace(/\/$/, "");
@@ -36,13 +50,12 @@ function toggleSearch(event: MouseEvent) {
 // 判断是否为外部链接
 function isExternalLink(link: string): boolean {
   const externalLinkPatterns = [/^https?:\/\//];
-
   return externalLinkPatterns.some((pattern) => pattern.test(link));
 }
 </script>
 
 <template>
-  <nav class="NavBar" :class="screenWidthStore.isAboveBreakpoint ? 'rail' : 'bar'">
+  <nav class="NavBar" :class="navMode">
     <button class="fab" @mousedown.prevent @click.stop="toggleSearch">
       <span>{{ searchStateStore.isSearchActive ? "close" : "search" }}</span>
     </button>