How do you handle loading and error states for data fetching in Next.js?

// app/products/loading.tsx → streamed fallback
export default function Loading() { return <Skeleton />; }

// app/products/page.tsx
import { notFound } from 'next/navigation';
export default async function Page() {
  const products = await getProducts();       // throw → caught by error.tsx
  if (products.length === 0) return <Empty />; // expected: handle inline
  return <Grid products={products} />;
}