 ```ts
export function mergeIntervals(intervals: number[][]): number[][] {
    if (!Array.isArray(intervals) || intervals.some(interval => interval.length !== 2)) {
        throw new Error("Input must be an array of exactly two-element arrays.");
    }

    if (intervals.some(([start, end]) => start > end)) {
        throw new Error("Each interval must have a start value less than or equal to its end value.");
    }

    // Sort intervals by their start times
    const sortedIntervals = [...intervals].sort((a, b) => a[0] - b[0]);

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

    for (let i = 1; i < sortedIntervals.length; i++) {
        const nextInterval = sortedIntervals[i];

        if (currentInterval[1] >= nextInterval[0]) {
            // Merge intervals if they overlap or touch
            currentInterval = [currentInterval[0], Math.max(currentInterval[1], nextInterval[1])];
        } else {
            // Push the non-overlapping interval to the result list
            merged.push(currentInterval);
            currentInterval = nextInterval;
        }
    }

    // Add the last interval after the loop
    if (currentInterval) {
        merged.push(currentInterval);
    }

    return merged;
}
```