/**
 * Load the last active chat ID from localStorage.
 * Safe: SSR guard, try/catch, validates format.
 */
export declare function loadLastActiveChatId(userId: string): string | null;
/**
 * Save the last active chat ID to localStorage.
 * Safe: SSR guard, try/catch. Pass undefined to clear.
 */
export declare function saveLastActiveChatId(userId: string, chatId: string | undefined): void;
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