dts -> ts -> dts

repro.ts

addEventListener("fetch", (e) => {
  const pathname = new URL(e.request.url).pathname;
  switch (pathname) {
    case "/foo.ts": {
      e.respondWith(new Response("export * from './bar'", {
        headers: {
          "content-type": "application/typescript",
        }
      }));
      return;
    }
    case "/bar": {
      e.respondWith(new Response("export {}", {
        headers: {
          "content-type": "application/typescript",
        }
      }));
      return;
    }
    default: {
      e.respondWith(new Response("404 Not Found", { status: 404 }));
      return;
    }
  }
});