feat: 内置阅读器、批注笔记与 AI 助手，发布 1.3.0

新增 PDF/EPUB/MOBI/AZW 内置阅读器，PDF 分段读取支持超大文件，
批注、读书与画布笔记、封面生成与本地导入。AI 助手支持三种协议、
图像上下文与安全 Markdown 渲染，上下文范围改为 选中/当前页/全文，
页面与全文无需选中文本即可发送，全文会提示可能超出模型限制。

便携版输出目录固定为 PeopleLib-windows-x64，不再随版本号变化，
避免升级后 data/ 被遗留在旧目录。

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/ui/ai-markdown.js

@@ -0,0 +1,96 @@
+(() => {
+  const MarkdownIt = window.markdownit;
+  const purifier = window.DOMPurify;
+  const MAX_MARKDOWN_LENGTH = 256 * 1024;
+
+  function safeExternalUrl(value) {
+    const raw = String(value || '').trim();
+    if (!/^https?:\/\//i.test(raw)) return '';
+    try {
+      const url = new URL(raw);
+      if (!/^https?:$/.test(url.protocol) || url.username || url.password) return '';
+      return url.toString();
+    } catch (error) {
+      return '';
+    }
+  }
+
+  if (typeof MarkdownIt !== 'function' || !purifier || typeof purifier.sanitize !== 'function') {
+    window.AiMarkdown = Object.freeze({
+      available: false,
+      mount(root, source) {
+        root.classList.add('ai-output-plain');
+        root.textContent = String(source || '');
+      },
+      externalUrl() {
+        return '';
+      }
+    });
+    return;
+  }
+
+  const markdown = new MarkdownIt({
+    html: false,
+    breaks: true,
+    linkify: true,
+    typographer: false
+  });
+
+  markdown.renderer.rules.link_open = (tokens, index, options, env, renderer) => {
+    const token = tokens[index];
+    const url = safeExternalUrl(token.attrGet('href'));
+    token.attrSet('href', '#');
+    if (url) {
+      token.attrSet('data-external-url', url);
+      token.attrSet('rel', 'noopener noreferrer');
+    } else {
+      token.attrJoin('class', 'ai-md-link-blocked');
+      token.attrSet('aria-disabled', 'true');
+    }
+    return renderer.renderToken(tokens, index, options);
+  };
+
+  markdown.renderer.rules.image = (tokens, index) => {
+    const alt = markdown.utils.escapeHtml(String(tokens[index].content || '').trim());
+    const label = alt ? `图片：${alt}` : '外部图片已阻止';
+    return `<span class="ai-md-image-placeholder" role="note">[${label}]</span>`;
+  };
+
+  const sanitizeOptions = Object.freeze({
+    ALLOWED_TAGS: [
+      'p', 'br', 'strong', 'em', 's', 'blockquote', 'pre', 'code',
+      'ul', 'ol', 'li', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6',
+      'table', 'thead', 'tbody', 'tr', 'th', 'td', 'hr', 'a', 'span'
+    ],
+    ALLOWED_ATTR: [
+      'href', 'title', 'class', 'rel', 'role', 'aria-disabled', 'data-external-url'
+    ],
+    ALLOW_DATA_ATTR: true,
+    ALLOW_ARIA_ATTR: true
+  });
+
+  function render(source) {
+    return purifier.sanitize(markdown.render(String(source || '')), sanitizeOptions);
+  }
+
+  window.AiMarkdown = Object.freeze({
+    available: true,
+    render,
+    mount(root, source) {
+      const text = String(source || '');
+      if (text.length > MAX_MARKDOWN_LENGTH) {
+        root.classList.add('ai-output-plain');
+        root.textContent = text;
+        return;
+      }
+      root.classList.remove('ai-output-plain');
+      root.innerHTML = render(text);
+    },
+    externalUrl(target) {
+      const link = target && typeof target.closest === 'function'
+        ? target.closest('a[data-external-url]')
+        : null;
+      return link ? safeExternalUrl(link.getAttribute('data-external-url')) : '';
+    }
+  });
+})();