/**
 * Date bucketing for the history overlay, mirroring TORUK Core's
 * `groupSessionsByDate` in `features/home/components/SessionsListPanel.jsx`.
 *
 * Kept out of the component so the rule can be tested on its own — the buckets
 * are the part with edge cases (midnight, the seven-day edge, a session that has
 * never been used, an unreadable timestamp), and none of that needs a DOM.
 */
import type { ChatSession } from '@/widget/controllers/createSessionStore';
import type { MessageKey } from '@/i18n';
export type HistoryBucket = {
    key: string;
    labelKey: MessageKey;
    items: ChatSession[];
};
/**
 * Bucket sessions by last activity, falling back to creation time.
 *
 * Two behaviours are Core's and deliberate: an unparseable timestamp lands in
 * Today rather than being dropped — a session the user can see must stay
 * reachable — and empty buckets are omitted so the list shows no bare headings.
 * Order within a bucket is left alone, because the store already sorted the list
 * by last activity descending.
 */
export declare function groupSessionsByDate(sessions: readonly ChatSession[]): HistoryBucket[];