/**
 * Attempt a silent token refresh using the stored refresh token.
 *
 * Uses a raw fetch (not the SDK API client) to avoid:
 *   1. Circular dependency: client → session → client
 *   2. Triggering the client's own 401 → tryRefreshSession loop
 *
 * Returns true if a new access token was obtained and stored.
 *
 * On network error the refresh token is NOT cleared — it may still be
 * valid once connectivity returns.  On 401/403 the token is cleared
 * because the server has explicitly rejected it (expired / revoked).
 */
export declare function tryRefreshSession(apiBaseUrl: string): Promise<boolean>;