/**
 * Filter incoming batch results to only those whose participantId
 * is not already in the set of existing result participantIds.
 */
export function filterNewResults(
  incoming: { participantId: string; placement: number }[],
  existingParticipantIds: Set<string>
): { participantId: string; placement: number }[] {
  return incoming.filter((r) => !existingParticipantIds.has(r.participantId));
}