/**
 * Return a string with millisecond precision removed from a PlainDateTime or PlainTime value.
 *
 * - Truncates to second precision.
 * - Accepts both PlainDateTime and PlainTime formats.
 * - Returns "" for invalid input.
 *
 * @param value ISO PlainDateTime or PlainTime string
 * @returns ISO string without milliseconds, or "" on invalid input
 *
 * @example chopMilliseconds("2024-02-29T12:34:56.789") // "2024-02-29T12:34:56"
 * @example chopMilliseconds("12:34:56.789") // "12:34:56"
 * @example chopMilliseconds("invalid") // ""
 */
export declare function chopMilliseconds(value: string): string;