/**
 * Ensures the xynginc binary exists.
 * It checks the custom path, the system PATH, and the local bin directory.
 * If not found and autoDownload is enabled, it downloads the binary.
 *
 * @param customPath - Optional custom path to the binary.
 * @param autoDownload - Whether to download the binary if missing.
 * @param version - The version to download.
 * @returns The absolute path to the binary.
 */
export declare function ensureBinary(customPath: string | undefined, autoDownload: boolean, version: string): Promise<string>;