/**
 * Return whether `value1` represents an instant strictly after `value2`.
 *
 * - Uses Temporal.Instant.compare for comparison.
 * - Returns false if either input is invalid.
 *
 * @param value1 first UTC datetime string
 * @param value2 second UTC datetime string
 * @returns `true` if `value1` is after `value2`, otherwise `false`
 *
 * @example isAfterUtc("2024-03-17T15:30:45Z", "2024-03-17T14:30:45Z") // true
 * @example isAfterUtc("2024-03-17T14:30:45Z", "2024-03-17T14:30:45Z") // false
 * @example isAfterUtc("2024-03-17T14:30:45Z", "invalid") // false
 */
export declare function isAfterUtc(value1: string, value2: string): boolean;