feat(compose): 正文内嵌隐藏块并升级 Markdown 编辑器

去掉整帖可见性表单，改为 :::hide 按块脱敏；工具栏补齐代码块、链接/图片对话框与粘贴拖拽上传。

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

frontend/lib/hideBlocks.ts

@@ -0,0 +1,154 @@
+/** 正文 :::hide 块解析（与 backend/markdown/hide.go 契约一致） */
+
+export type HideKind = "login" | "reply" | "points";
+
+export type HideSegment =
+  | { type: "md"; text: string }
+  | {
+      type: "hide";
+      kind: HideKind;
+      points: number;
+      locked: boolean;
+      body: string;
+    };
+
+const OPEN_RE = /^:::hide\s+(login|reply|points)(?:\s+(\d+))?(?:\s+(locked))?\s*$/;
+
+function isClose(line: string): boolean {
+  return line.trim() === ":::";
+}
+
+function parseOpen(trimmed: string): {
+  kind: HideKind;
+  points: number;
+  locked: boolean;
+} | null {
+  const m = OPEN_RE.exec(trimmed);
+  if (!m) return null;
+  const kind = m[1] as HideKind;
+  const points = m[2] ? Number(m[2]) : 0;
+  const locked = m[3] === "locked";
+  if (kind === "points" && (!Number.isFinite(points) || points < 1)) {
+    return null;
+  }
+  return { kind, points: kind === "points" ? points : 0, locked };
+}
+
+/**
+ * 将正文拆成公开 Markdown 段与隐藏块（忽略代码围栏内伪语法）。
+ * 解析失败时整篇当作普通 Markdown，避免渲染崩溃。
+ */
+export function splitHideSegments(content: string): HideSegment[] {
+  if (!content) return [{ type: "md", text: "" }];
+  const lines = content.replace(/\r\n/g, "\n").replace(/\r/g, "\n").split("\n");
+  const out: HideSegment[] = [];
+  let buf: string[] = [];
+  let inCode = false;
+  let i = 0;
+
+  const flushMd = () => {
+    if (buf.length === 0) return;
+    out.push({ type: "md", text: buf.join("\n") });
+    buf = [];
+  };
+
+  while (i < lines.length) {
+    const trimmed = lines[i].trim();
+    if (trimmed.startsWith("```")) {
+      inCode = !inCode;
+      buf.push(lines[i]);
+      i++;
+      continue;
+    }
+    if (inCode) {
+      buf.push(lines[i]);
+      i++;
+      continue;
+    }
+
+    const open = parseOpen(trimmed);
+    if (open) {
+      flushMd();
+      const bodyLines: string[] = [];
+      let j = i + 1;
+      let innerCode = false;
+      let found = false;
+      while (j < lines.length) {
+        const inner = lines[j].trim();
+        if (inner.startsWith("```")) {
+          innerCode = !innerCode;
+          bodyLines.push(lines[j]);
+          j++;
+          continue;
+        }
+        if (innerCode) {
+          bodyLines.push(lines[j]);
+          j++;
+          continue;
+        }
+        if (parseOpen(inner)) {
+          // 嵌套：放弃隐藏语义，整段当普通文本
+          buf.push(lines[i]);
+          i++;
+          found = false;
+          break;
+        }
+        if (isClose(inner)) {
+          found = true;
+          break;
+        }
+        bodyLines.push(lines[j]);
+        j++;
+      }
+      if (!found) {
+        // 未闭合：开标记行起当普通文本
+        buf.push(lines[i]);
+        i++;
+        continue;
+      }
+      out.push({
+        type: "hide",
+        kind: open.kind,
+        points: open.points,
+        locked: open.locked,
+        body: bodyLines.join("\n"),
+      });
+      i = j + 1;
+      continue;
+    }
+
+    buf.push(lines[i]);
+    i++;
+  }
+  flushMd();
+  return out.length > 0 ? out : [{ type: "md", text: content }];
+}
+
+/** 去掉锁块与标记后，供 SEO / TOC / description 使用的公开纯文本片段 */
+export function publicMarkdownForSeo(content: string): string {
+  const segs = splitHideSegments(content);
+  return segs
+    .filter((s): s is Extract<HideSegment, { type: "md" }> => s.type === "md")
+    .map((s) => s.text)
+    .concat(
+      segs
+        .filter(
+          (s): s is Extract<HideSegment, { type: "hide" }> =>
+            s.type === "hide" && !s.locked
+        )
+        .map((s) => s.body)
+    )
+    .join("\n\n")
+    .trim();
+}
+
+export function hideKindLabel(kind: HideKind): string {
+  switch (kind) {
+    case "login":
+      return "登录可见";
+    case "reply":
+      return "回复可见";
+    case "points":
+      return "积分可见";
+  }
+}