feat: 代码片段功能与 Markdown 内嵌片段渲染、文档截图等

frontend/lib/directiveBlocks.ts

@@ -27,7 +27,8 @@ export type ContentSegment =
   | { type: "timeline"; items: TimelineItem[]; rawBody: string }
   | { type: "entries"; items: EntryItem[]; rawBody: string }
   | { type: "details"; title: string; body: string }
-  | { type: "video"; provider: "bilibili" | "youtube"; id: string };
+  | { type: "video"; provider: "bilibili" | "youtube"; id: string }
+  | { type: "snippet"; id: number };
 
 function isTimelineClose(line: string): boolean {
   return line.trim().toLowerCase() === "[/timeline]";
@@ -57,6 +58,18 @@ export function parseDetailsOpen(trimmed: string): string {
   return title || DETAILS_DEFAULT_TITLE;
 }
 
+/* ---------- [snippet id=N] 代码片段嵌入（整行单标记） ---------- */
+
+const SNIPPET_LINE_RE = /^\[snippet\s+id=(\d+)\]$/i;
+
+/** 整行 `[snippet id=N]`。解析失败返回 null（该行按普通 Markdown 处理）。 */
+export function parseSnippetLine(trimmed: string): number | null {
+  const m = trimmed.match(SNIPPET_LINE_RE);
+  if (!m) return null;
+  const id = Number(m[1]);
+  return Number.isInteger(id) && id > 0 ? id : null;
+}
+
 /* ---------- [bilibili] / [youtube] 视频嵌入（整行单标记） ---------- */
 
 const VIDEO_LINE_RE = /^\[(bilibili|youtube)\]([^\[\]]+)\[\/\1\]$/i;
@@ -122,6 +135,7 @@ export function splitContentSegments(
     | { type: "entries"; body: string }
     | { type: "details"; title: string; body: string }
     | { type: "video"; provider: "bilibili" | "youtube"; id: string }
+    | { type: "snippet"; id: number }
   > = [];
   let buf: string[] = [];
   let inCode = false;
@@ -228,6 +242,15 @@ export function splitContentSegments(
       continue;
     }
 
+    // [snippet id=N] 整行片段嵌入
+    const snippetId = parseSnippetLine(trimmed);
+    if (snippetId != null) {
+      flushMd();
+      raw.push({ type: "snippet", id: snippetId });
+      i++;
+      continue;
+    }
+
     // [entries:off] 例外块：body 原样进 md 缓冲（标记行丢弃），
     // 不再参与 entries/timeline 拆分；未闭合时整块当普通 Markdown
     if (isEntriesOffOpen(trimmed)) {
@@ -273,6 +296,10 @@ export function splitContentSegments(
       out.push({ type: "video", provider: part.provider, id: part.id });
       continue;
     }
+    if (part.type === "snippet") {
+      out.push({ type: "snippet", id: part.id });
+      continue;
+    }
     const hideSegs = splitHideSegments(part.text) as HideSegment[];
     for (const s of hideSegs) {
       if (s.type === "md") {