/**
 * Validates whether a given value is a valid hexadecimal string.
 *
 * A valid hexadecimal string:
 * - Contains only characters 0-9, a-f, or A-F
 * - Can optionally start with "0x" or "0X" prefix
 * - Must have at least one hex digit after any prefix
 * - Can be of any length (after prefix)
 *
 * @param value - The value to check (can be any type)
 * @returns true if the value is a valid hexadecimal string, false otherwise
 *
 * @example
 * isHexadecimal("1a2b3c") // true
 * isHexadecimal("0xFFFF") // true
 * isHexadecimal("GHI") // false
 * isHexadecimal("0x") // false
 * isHexadecimal("") // false
 * isHexadecimal(123) // false
 * @returns true if the value is a valid hexadecimal string, false otherwise
 * @since 1.0.1
 */
export declare function isHexadecimal(value: unknown): boolean;