export declare function logPrefix(opts: {
    isTTY: boolean;
    envFlag: string | undefined;
    now: Date;
}): string;
export declare function logInfo(message: string): void;
export declare function logSuccess(message: string): void;
export declare function logWarn(message: string): void;
export declare function logError(message: string): void;
export declare function formatElapsed(ms: number): string;
export declare function startHeartbeat(label: string, intervalMs?: number): {
    stop: () => void;
    touch: () => void;
};