/**
 * Return true when `pointOrStart` falls within the interval `[intervalStart, intervalEnd]`
 * (3-arg), or when the inner interval `[innerStart, innerEnd]` is fully contained within
 * the outer interval `[intervalStart, intervalEnd]` (4-arg).
 *
 * - Compares numeric Unix epoch values directly.
 * - Always-inclusive boundaries: `start <= point <= end`.
 * - Returns `false` if `intervalStart > intervalEnd` (invalid outer interval).
 * - Returns `false` if `innerStart > innerEnd` in 4-arg mode (invalid inner interval).
 * - Returns `false` on invalid input (non-numeric types, non-finite values).
 *
 * @param intervalStart Unix epoch value (seconds or milliseconds) — outer interval start
 * @param intervalEnd Unix epoch value (seconds or milliseconds) — outer interval end
 * @param pointOrStart Unix epoch value for the point (3-arg) or inner start (4-arg)
 * @param pointEnd optional Unix epoch value for the inner interval end (4-arg mode)
 * @returns true if the point or inner interval is contained, or false on invalid input
 *
 * @example intervalContainsUnix(0, 1700000000, 170000000) // true
 * @example intervalContainsUnix(0, 1700000000, 170000000, 1500000000) // true
 * @example intervalContainsUnix(1700000000, 0, 170000000) // false
 * @example intervalContainsUnix(0, 1700000000, 170000000, 15000000) // false
 * @example intervalContainsUnix(NaN, 1700000000, 170000000) // false
 * @example intervalContainsUnix("0", "1700000000", "170000000") // true
 */
export declare function intervalContainsUnix(intervalStart: number | string, intervalEnd: number | string, pointOrStart: number | string, pointEnd?: number | string): boolean;