```typescript
export function chunk<T>(items: readonly T[], size: number): T[][] {
  if (size <= 0 || !Number.isInteger(size)) {
    throw new Error("Size must be a positive integer.");
  }

  const result: T[][] = [];
  const numGroups = Math.ceil(items.length / size);

  for (let i = 0; i < numGroups; i++) {
    const start = i * size;
    const end = Math.min(start + size, items.length);
    result.push(items.slice(start, end));
  }

  return result;
}
```