feat: add export-to-PDF via browser print with @media print CSS

webapp/static/js/report.js

@@ -286,4 +286,22 @@ const Report = {
 
     body.innerHTML = `<div class="advice-md">${html}</div>`;
   },
+
+  // 导出 PDF：展开所有低分样本 → 打印 → 还原折叠状态
+  exportPdf() {
+    // 1. 记录当前各 detail 展开状态，并全部展开
+    const details = document.querySelectorAll("#lowest-table .lowest-detail");
+    const wasHidden = Array.from(details).map((el) => el.hidden);
+    details.forEach((el) => { el.hidden = false; });
+
+    // 2. 打印完成后还原折叠状态
+    const restore = () => {
+      details.forEach((el, i) => { el.hidden = wasHidden[i]; });
+      window.removeEventListener("afterprint", restore);
+    };
+    window.addEventListener("afterprint", restore);
+
+    // 3. 触发打印（浏览器弹出打印对话框，用户选"另存为 PDF"）
+    window.print();
+  },
 };