/**
 * Keep the usage snapshot alive while any session is running.
 *
 * The snapshot feeds rotation targeting (which account still has room on THIS
 * model) and the dashboard, and refreshing it is also what renews idle
 * profiles' logins before they rot. It used to be refreshed only by the
 * proactive-rotation loop, which is a FEATURE, off by default. With proactive
 * off and no dashboard open, nothing refreshed anything: the snapshot found
 * tonight was ten hours stale while seven sessions ran, so rotation was
 * choosing targets from the morning's numbers and idle profiles were quietly
 * dying of old age.
 *
 * Watching data is not a feature to opt into; it is the floor. This runner is
 * mounted for every interactive session, and stays cheap two ways:
 *
 * - fresh-enough: when the snapshot is younger than half the interval, there
 *   is nothing worth asking. This is what keeps N concurrent sessions from
 *   multiplying the probes: whoever refreshed last covered everyone.
 * - one at a time: a try-lock, never waited on. A busy lock means another
 *   session is refreshing right now, which is the freshest answer available.
 */
export type RefreshOutcome = 'refreshed' | 'fresh-enough' | 'busy' | 'error';
export interface UsageRefresherDeps {
    /** Run one full refresh (probe every account, write the snapshot). */
    refresh: () => Promise<unknown>;
    /** How old the stored snapshot is, in ms; Infinity when there is none. */
    snapshotAgeMs: () => number;
    /** Try to become the one refresher; never waits. */
    tryLock: () => {
        held: boolean;
        release: () => void;
    };
    /** Told what each tick decided, with the evidence. */
    onOutcome?: (outcome: RefreshOutcome, detail: {
        ageMs: number;
        error?: string;
    }) => void;
    now?: () => number;
}
/** One decision + refresh cycle. Exported so the policy is testable alone. */
export declare function refresherTick(deps: UsageRefresherDeps, intervalMs: number): Promise<RefreshOutcome>;
export interface UsageRefresher {
    stop(): void;
}
/**
 * Run {@link refresherTick} for the lifetime of a session. The first tick runs
 * right away, because the most common reason to need one is a snapshot nobody
 * has touched for hours. The timer is unref'd so it can never keep the process
 * alive on its own.
 */
export declare function startUsageRefresher(deps: UsageRefresherDeps, intervalMs: number): UsageRefresher;