/**
 * Merges override values into a base string map, skipping `undefined` entries.
 *
 * @typeParam TBase - Base map type to preserve in the merged result.
 * @param base - Base key/value map.
 * @param overrides - Optional override map where `undefined` means "no change".
 * @returns Object with merged map and list of keys that were actually applied.
 * @category Theme
 */
export declare function mergeOverrides<TBase extends Record<string, string>>(base: TBase, overrides?: Record<string, string | undefined>): {
    merged: TBase;
    appliedKeys: string[];
};