feat: 公文三栏单页布局，并修复时间线目录跳转与样式

公告/单页对齐帖子详情三栏壳；时间线按日锚点可跳转，条目改为日志行并用暖金日期区分 feat 色。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/post/[id]/page.tsx

@@ -29,7 +29,7 @@ import { getMeCached, getPublicSettingsCached } from "@/lib/serverData";
 import CommentSection from "@/components/CommentSection";
 import PostActions from "@/components/PostActions";
 import LikeButton from "@/components/LikeButton";
-import PostToc, { type TocItem } from "@/components/PostToc";
+import PostToc from "@/components/PostToc";
 import MobilePostBar from "@/components/MobilePostBar";
 import Avatar from "@/components/Avatar";
 import RoleBadge from "@/components/RoleBadge";
@@ -41,6 +41,7 @@ import AcceptedAnswerCard from "@/components/AcceptedAnswerCard";
 import { canModerateBoard } from "@/lib/roles";
 import { IconComment, IconEye } from "@/components/Icons";
 import { normalizePostType, postTypeLabel, contentAccessLabel, typeStatusLabel, typeStatusClass } from "@/lib/postMeta";
+import { extractToc, estimateReadingMinutes, markdownHeadingToc } from "@/lib/toc";
 
 interface PageProps {
   params: Promise<{ id: string }>;
@@ -78,26 +79,6 @@ export async function generateMetadata({ params }: PageProps): Promise<Metadata>
   }
 }
 
-/**
- * 从 Markdown 提取二三级标题生成目录项，id 按出现顺序编号；
- * 代码围栏内的 # 不计入
- */
-function extractToc(content: string): TocItem[] {
-  const items: TocItem[] = [];
-  let inCode = false;
-  for (const raw of content.split(/\r?\n/)) {
-    const line = raw.trim();
-    if (line.startsWith("```")) {
-      inCode = !inCode;
-      continue;
-    }
-    if (inCode) continue;
-    const m = /^(#{2,3})\s+(.+?)\s*#*\s*$/.exec(line);
-    if (m) items.push({ level: m[1].length as 2 | 3, text: m[2], id: `h-${items.length}` });
-  }
-  return items;
-}
-
 function formatYMD(dateStr: string) {
   const d = new Date(dateStr);
   return `${d.getFullYear()}.${String(d.getMonth() + 1).padStart(2, "0")}.${String(
@@ -484,10 +465,8 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
 
   const publicBody = publicMarkdownForSeo(post.content || "");
   const toc = extractToc(publicBody);
-  const readingMinutes = Math.max(
-    1,
-    Math.ceil((publicBody.length > 0 ? publicBody.length : post.title.length) / 400)
-  );
+  const headingToc = markdownHeadingToc(toc);
+  const readingMinutes = estimateReadingMinutes(publicBody, post.title.length);
   const edited =
     new Date(post.updated_at).getTime() - new Date(post.created_at).getTime() > 60_000;
 
@@ -559,11 +538,11 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
       }),
   };
 
-  // 目录项与 Markdown 标题按渲染顺序一一对应（extractToc 顺序 == 文档顺序）
+  // 仅正文 Markdown 标题与 headingRenderer 按序对应（时间线日锚点另有 tl-* id）
   let headingIndex = 0;
   const headingRenderer = (Tag: "h2" | "h3") =>
     function Heading({ children }: { children?: React.ReactNode }) {
-      const item = toc[headingIndex++];
+      const item = headingToc[headingIndex++];
       return (
         <Tag id={item?.id} style={{ scrollMarginTop: 90 }}>
           {children}