/**
 * Return true if `start` and `end` form a valid Unix interval — both finite numbers
 * and `start <= end`.
 *
 * - Both inputs must be numbers (or numeric strings that coerce to finite numbers).
 * - Equal `start === end` is valid.
 * - Non-finite values (NaN, Infinity) return `false`.
 *
 * @param start Unix epoch value (seconds or milliseconds) — interval start
 * @param end Unix epoch value (seconds or milliseconds) — interval end
 * @returns true if start and end form a valid Unix interval, or false on invalid input
 *
 * @example isValidUnixInterval(0, 1700000000) // true
 * @example isValidUnixInterval(1000, 1000) // true
 * @example isValidUnixInterval(1700000000, 0) // false
 * @example isValidUnixInterval("0", "1700000000") // true
 */
export declare function isValidUnixInterval(start: number | string, end: number | string): boolean;