/**
 * Slack Credentials Persistence Service
 *
 * Persists Slack tokens to ~/.crewly/slack-credentials.json so that
 * tokens configured via the /settings UI survive server restarts.
 * The file is written with 0600 permissions to protect secrets.
 *
 * @module services/slack/slack-credentials
 */
import { SlackConfig } from '../../types/slack.types.js';
/**
 * Save Slack credentials to disk with restricted file permissions (0600).
 *
 * @param config - The SlackConfig to persist.
 */
export declare function saveSlackCredentials(config: SlackConfig): Promise<void>;
/**
 * Load saved Slack credentials from disk.
 *
 * @returns SlackConfig if credentials file exists and is valid, null otherwise.
 */
export declare function loadSlackCredentials(): Promise<SlackConfig | null>;
/**
 * Delete saved Slack credentials from disk.
 */
export declare function deleteSlackCredentials(): Promise<void>;
/**
 * Check if saved Slack credentials exist on disk.
 *
 * @returns True if the credentials file exists.
 */
export declare function hasSavedCredentials(): Promise<boolean>;
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