```ts
/**
 * Split an array into consecutive groups of at most size elements.
 * @param items - The array to split.
 * @param size - The maximum size of each group.
 * @returns An array of groups, each with up to 'size' elements.
 */
export function chunk<T>(items: readonly T[], size: number): T[][] {
    if (!Number.isInteger(size) || size <= 0) {
        throw new Error('Size must be a positive integer.');
    }

    if (items.length === 0) {
        return [];
    }

    const result: T[][] = [];
    for (let i = 0; i < items.length; i += size) {
        result.push(items.slice(i, i + size));
    }
    return result;
}
```