feat: 代码片段功能与 Markdown 内嵌片段渲染、文档截图等

frontend/components/Header.tsx

@@ -20,6 +20,7 @@ import {
   MessageSquare,
   X,
   ExternalLink,
+  CodeXml,
 } from "lucide-react";
 import { apiLogout, apiMe, apiChatUnreadSummary, type User } from "@/lib/api";
 import { hasAuthCookieHint } from "@/lib/cookies";
@@ -37,7 +38,7 @@ import BadgeChip from "./BadgeChip";
 import BrandLockup from "./BrandLockup";
 import { useAllowMessages } from "./MessagesPolicyProvider";
 import { useSiteBrand, useUrlStyle } from "./SiteBrandProvider";
-import { leaderboardPath, libraryPath } from "@/lib/urlStyle";
+import { leaderboardPath, libraryPath, snippetsPath } from "@/lib/urlStyle";
 import {
   HEADER_NAV_BUILTIN_LABELS,
   isHeaderNavExternal,
@@ -84,6 +85,7 @@ export default function Header({
   const urlStyle = useUrlStyle();
   const lbHref = leaderboardPath(urlStyle);
   const libHref = libraryPath(urlStyle);
+  const snipHref = snippetsPath(urlStyle);
   // 顶部主导航由后台「基本信息 → 顶部导航」配置（顺序/显隐/自定义链接），
   // 配置为空时整个 nav 不渲染（含左侧分隔线）；移动端导航走底部公共菜单
   const headerNav = useSiteBrand().header_nav;
@@ -91,16 +93,22 @@ export default function Header({
     home: <Home size={15} />,
     leaderboard: <Trophy size={15} />,
     library: <BookOpen size={15} />,
+    snippets: <CodeXml size={15} />,
   };
   const builtinNavHref: Record<HeaderNavBuiltinKey, string> = {
     home: "/",
     leaderboard: lbHref,
     library: libHref,
+    snippets: snipHref,
   };
   const isBuiltinNavActive = (key: HeaderNavBuiltinKey): boolean => {
     if (!pathname) return false;
     if (key === "home") return pathname === "/";
     if (key === "leaderboard") return pathname === lbHref || pathname.startsWith(`${lbHref}/`);
+    if (key === "snippets") {
+      // 片段详情标准路径与伪静态（/snippet-*.html）统一按前缀高亮
+      return pathname.startsWith("/snippets") || pathname.startsWith("/snippet-");
+    }
     // 书库详情/阅读页标准路径与伪静态（/library-*.html）统一按 /library 前缀高亮
     return pathname.startsWith("/library");
   };