/**
 * Deep merges multiple objects into the target object.
 * Arrays are overwritten, not concatenated.
 *
 * @param target The target object to merge into.
 * @param sources The source objects to merge from.
 * @returns The merged target object.
 */
export declare function deepMerge<T extends Record<string, unknown>>(target: T, ...sources: Partial<T>[]): T;
/**
 * Checks if a value is a plain object.
 *
 * @param item The value to check.
 * @returns True if the value is a plain object, false otherwise.
 */
export declare function isObject(item: unknown): item is Record<string, unknown>;