/**
 * 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).
 *
 * - Uses `Temporal.Instant.compare` for comparison (same instant semantics).
 * - 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 (wrong type, malformed strings, leap seconds).
 *
 * @param intervalStart ISO 8601 UTC datetime string for the outer interval start
 * @param intervalEnd ISO 8601 UTC datetime string for the outer interval end
 * @param pointOrStart ISO 8601 UTC datetime string for the point (3-arg) or inner start (4-arg)
 * @param pointEnd optional ISO 8601 UTC datetime string for the inner interval end (4-arg mode)
 * @returns true if the point or inner interval is contained, or false on invalid input
 *
 * @example intervalContainsUtc("2024-01-01T00:00:00Z", "2024-12-31T23:59:59Z", "2024-06-15T12:00:00Z") // true
 * @example intervalContainsUtc("2024-01-01T00:00:00Z", "2024-12-31T23:59:59Z", "2024-06-15T12:00:00Z", "2024-07-15T12:00:00Z") // true
 * @example intervalContainsUtc("2024-12-31T23:59:59Z", "2024-01-01T00:00:00Z", "2024-06-15T12:00:00Z") // false
 * @example intervalContainsUtc("invalid", "2024-12-31T23:59:59Z", "2024-06-15T12:00:00Z") // false
 */
export declare function intervalContainsUtc(intervalStart: string, intervalEnd: string, pointOrStart: string, pointEnd?: string): boolean;