```ts
export function chunk<T>(items: readonly T[], size: number): T[][] {
  if (typeof size !== 'number' || size <= 0) {
    throw new Error('size must be a positive integer');
  }
  if (items.length === 0) return [];

  const result: T[][] = [];
  let start = 0;

  while (start < items.length) {
    const end = Math.min(start + size, items.length);
    result.push(items.slice(start, end));
    start += size;
  }

  return result;
}
```