import { useMemo } from "react";import { inferCheckpointTurnCountByTurnId } from "../session-logic";import type { Thread, TurnDiffSummary } from "../types"; export function useTurnDiffSummaries(activeThread: Thread | null | undefined) {  const turnDiffSummaries = useMemo<ReadonlyArray<TurnDiffSummary>>(() => {    if (!activeThread) {      return [];    }    return activeThread.checkpoints;  }, [activeThread]);   const inferredCheckpointTurnCountByTurnId = useMemo(    () => inferCheckpointTurnCountByTurnId(turnDiffSummaries),    [turnDiffSummaries],  );   return { turnDiffSummaries, inferredCheckpointTurnCountByTurnId };}