```ts
/**
 * Merges overlapping intervals into the smallest list of non-overlapping pairs.
 * @param intervals - List of [start, end] pairs to merge.
 * @returns Sorted list of merged [start, end] pairs.
 */
export function mergeIntervals(intervals: number[][]): number[][] {
    if (intervals.length === 0) return [];

    const sortedIntervals = intervals
        .filter(([start, end]) => start <= end)
        .sort((a, b) => a[0] - b[0]);

    let merged: number[][] = [sortedIntervals[0]];

    for (let i = 1; i < sortedIntervals.length; i++) {
        const lastMerged = merged[merged.length - 1];
        const current = sortedIntervals[i];

        if (current[0] <= lastMerged[1]) {
            merged[merged.length - 1] = [lastMerged[0], Math.max(lastMerged[1], current[1])];
        } else {
            merged.push(current);
        }
    }

    return merged;
}
```