/**
 * Wrap a user-supplied store into the interface the rate-limit algorithms
 * expect. Validates that the required methods exist so misconfigurations
 * surface at startup, not at the first blocked request.
 *
 * Required methods (all may be async):
 *   - `get(key)`                  → { count, expiresAt } | null
 *   - `incr(key, ttlMs)`          → { count, expiresAt }   (atomic)
 *   - `set(key, count, ttlMs)`    → void
 *   - `delete(key)`               → void
 *
 * Optional:
 *   - `reset(key)`                → void (defaults to `delete`)
 *   - `decr(key)`                 → void — atomic decrement of an existing
 *     key. When provided, `sliding` uses it for race-free rollback of a
 *     rejected request's tentative increment.
 *   - `compareAndSet(key, expected, value, ttlMs)` → boolean — atomic CAS
 *     (`expected: null` = key must not exist). When provided,
 *     `tokenBucket` / `leakyBucket` become race-free under concurrency.
 *
 * Atomicity guarantee: `incr` must be atomic across concurrent callers. On
 * Redis, wrap `INCR + EXPIRE` in a Lua script or MULTI/EXEC. On Mongo, use
 * `findOneAndUpdate` with upsert. Non-atomic implementations race and let
 * requests bypass the limit under load.
 *
 * @param {Partial<import('../index.js').RateLimitStore>} impl
 * @returns {import('../index.js').RateLimitStore}
 */
export function customStore(impl: Partial<import("../index.js").RateLimitStore>): import("../index.js").RateLimitStore;