/**
 * Return the current microsecond for the specified IANA timeZone.
 *
 * - Uses Temporal.Now.zonedDateTimeISO to get the current time.
 * - Validation is performed on the timezone.
 *
 * @param ianaTimezone IANA timeZone identifier
 * @returns current microsecond string (zero-padded to 3 digits) or "" on invalid input
 *
 * @example getZonedMicrosecond("America/New_York") // "000"
 * @example getZonedMicrosecond("invalid") // ""
 */
export declare function getZonedMicrosecond(ianaTimezone: string): string;