完善 TipTap 编辑器与个人资料页：头像裁剪、Tab 缩进、文章内链、Markdown 工具与 Tooltip，并更新样式与 Feed 缓存。

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

frontend/src/utils/markdownFormat.ts

@@ -0,0 +1,109 @@
+import { applyTextareaChange } from './markdownIndent';
+
+type ChangeHandler = (value: string) => void;
+
+/** 在选区两侧包裹 Markdown 标记 */
+export function wrapMarkdownSelection(
+  textarea: HTMLTextAreaElement,
+  value: string,
+  prefix: string,
+  suffix: string,
+  placeholder: string,
+  onChange: ChangeHandler,
+) {
+  const { selectionStart, selectionEnd } = textarea;
+  const selected = value.slice(selectionStart, selectionEnd);
+  const text = selected || placeholder;
+  const insert = prefix + text + suffix;
+  const next = value.slice(0, selectionStart) + insert + value.slice(selectionEnd);
+  const newStart = selectionStart + prefix.length;
+  const newEnd = newStart + text.length;
+  applyTextareaChange(textarea, next, newStart, newEnd, onChange);
+}
+
+/** 为当前行或选区行添加前缀（如引用） */
+export function prefixMarkdownLines(
+  textarea: HTMLTextAreaElement,
+  value: string,
+  prefix: string,
+  onChange: ChangeHandler,
+) {
+  const { selectionStart, selectionEnd } = textarea;
+  const lineStart = value.lastIndexOf('\n', selectionStart - 1) + 1;
+  const nextNewline = value.indexOf('\n', selectionEnd);
+  const lineEnd = nextNewline === -1 ? value.length : nextNewline;
+  const block = value.slice(lineStart, lineEnd);
+  const lines = block.split('\n').map(line => `${prefix}${line}`);
+  const next = value.slice(0, lineStart) + lines.join('\n') + value.slice(lineEnd);
+  applyTextareaChange(
+    textarea,
+    next,
+    selectionStart + prefix.length,
+    selectionEnd + prefix.length * lines.length,
+    onChange,
+  );
+}
+
+/** 切换当前行标题级别（源码模式） */
+export function cycleMarkdownHeading(
+  textarea: HTMLTextAreaElement,
+  value: string,
+  onChange: ChangeHandler,
+) {
+  const { selectionStart } = textarea;
+  const lineStart = value.lastIndexOf('\n', selectionStart - 1) + 1;
+  const lineEnd = value.indexOf('\n', selectionStart);
+  const end = lineEnd === -1 ? value.length : lineEnd;
+  const line = value.slice(lineStart, end);
+  const match = line.match(/^(#{2,6})\s+(.*)$/);
+  let nextLine: string;
+  if (!match) {
+    nextLine = `## ${line}`;
+  } else {
+    const level = match[1].length;
+    const body = match[2];
+    nextLine = level >= 6 ? body : `${'#'.repeat(level + 1)} ${body}`;
+  }
+  const next = value.slice(0, lineStart) + nextLine + value.slice(end);
+  const offset = nextLine.length - line.length;
+  applyTextareaChange(
+    textarea,
+    next,
+    selectionStart + Math.max(0, offset),
+    selectionStart + Math.max(0, offset),
+    onChange,
+  );
+}
+
+/** 插入登录可见区块模板 */
+export function insertMarkdownMembersOnly(
+  textarea: HTMLTextAreaElement,
+  value: string,
+  onChange: ChangeHandler,
+) {
+  const { selectionStart, selectionEnd } = textarea;
+  const snippet = '\n\n<members-only>\n\n\n</members-only>\n\n';
+  const next = value.slice(0, selectionStart) + snippet + value.slice(selectionEnd);
+  const cursor = selectionStart + '\n\n<members-only>\n\n'.length;
+  applyTextareaChange(textarea, next, cursor, cursor, onChange);
+}
+
+/** 在光标处插入链接 Markdown */
+export function insertMarkdownLink(
+  textarea: HTMLTextAreaElement,
+  value: string,
+  url: string,
+  onChange: ChangeHandler,
+) {
+  const { selectionStart, selectionEnd } = textarea;
+  const selected = value.slice(selectionStart, selectionEnd) || '链接文字';
+  const insert = `[${selected}](${url})`;
+  const next = value.slice(0, selectionStart) + insert + value.slice(selectionEnd);
+  applyTextareaChange(
+    textarea,
+    next,
+    selectionStart + insert.length,
+    selectionStart + insert.length,
+    onChange,
+  );
+}