fix: monaco-editor offline build error

frontend/scripts/copy-monaco.mjs

@@ -0,0 +1,40 @@
+// 把 monaco-editor 自带的预构建 min/vs 复制到 public/monaco/vs,
+// 让 @monaco-editor/react 的 loader 在离线环境下从同源 /monaco/vs 加载,
+// 不再依赖 jsDelivr CDN。postinstall 时跑一次即可,产物不进 git(被 .gitignore
+// 忽略),由 pnpm install 重新生成。
+
+import { cp, mkdir, rm, stat } from "node:fs/promises";
+import { dirname, join, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const here = dirname(fileURLToPath(import.meta.url));
+const frontendRoot = resolve(here, "..");
+
+const src = resolve(
+  frontendRoot,
+  "node_modules/monaco-editor/min/vs",
+);
+const dest = resolve(frontendRoot, "public/monaco/vs");
+
+async function exists(p) {
+  try {
+    await stat(p);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+if (!(await exists(src))) {
+  console.error(
+    `[copy-monaco] 源目录不存在: ${src}\n` +
+      `请确认 frontend/package.json 已声明 monaco-editor 依赖并已 pnpm install。`,
+  );
+  process.exit(1);
+}
+
+await mkdir(dirname(dest), { recursive: true });
+await rm(dest, { recursive: true, force: true });
+await cp(src, dest, { recursive: true });
+
+console.log(`[copy-monaco] ${src} -> ${dest}`);