feat: add agent-first minitool studio MVP

lib/http.ts

@@ -0,0 +1,7 @@
+import { NextResponse } from "next/server";
+
+export function errorResponse(error: unknown) {
+  const value = error as Error & { status?: number; code?: string };
+  const status = value.status || (value.code === "ENOENT" ? 404 : 400);
+  return NextResponse.json({ error: value.message || "Unknown error" }, { status });
+}