/**
 * Create a shell snapshot, caching the result.
 * Returns the path to the snapshot file, or null if creation failed.
 *
 * Concurrent callers share one in-flight creation. A failure is remembered
 * for {@link SNAPSHOT_FAILURE_RETRY_MS} (or until the rc file or the
 * environment changes), so a slow or broken rc costs one spawn instead of one
 * per bash call.
 *
 * `timeoutMs` is configurable so callers exercising failure handling do not
 * have to wait out the production startup budget.
 */
export declare function getOrCreateSnapshot(shell: string, env: Record<string, string | undefined>, timeoutMs?: number): Promise<string | null>;