/**
 * Shared map-building utilities
 */
/**
 * Build a Map from an array using a key function.
 * When duplicate keys occur, the last item wins.
 */
export declare function buildLookupMap<T>(items: readonly T[], keyFn: (item: T) => string): Map<string, T>;
/**
 * Build a Map grouping items by a key function.
 * Items where keyFn returns undefined are skipped.
 */
export declare function buildGroupMap<T>(items: readonly T[], keyFn: (item: T) => string | undefined): Map<string, T[]>;