/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
import { type LoadedSettings } from '../config/settings.js';
/**
 * Validates the configured theme.
 * @param settings The loaded application settings.
 * @returns An error message if the theme is not found, otherwise null.
 */
export declare function validateTheme(settings: LoadedSettings): string | null;