Per-listing answer references carried through a checkout, shared by the booking and checkout intents.
optional
listingAnswerIds: Record<string, number[]> | undefined
Per-listing answer IDs: maps listingId → answerIds for that listing's questions
optional
listingTextAnswerIds: Record<string, TextAnswerRef[]> | undefined
Per-listing free-text string refs: maps listingId → question/string ids.