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

    const result: T[][] = [];
    for (let i = 0; i < items.length; i += size) {
        // Use slice to get each chunk of length 'size'
        result.push([...items.slice(i, i + size)]);
    }
    return result;
}
```