A piece of the answer's text. Append in order.
A tool started. A new block of text may follow it.
Something to show with the answer being streamed (products, an order, tracking).
The assistant changed the shopper's cart: reload it. cartAccessToken is set only when the
assistant had to create the cart; store it with cartId exactly as after cart.create().
A card for the shopper to confirm or decline.
Suggested replies for the answer just streamed (2–4 short texts). Sent at most once per turn,
before done; replaces any shown earlier. Also on the message in conversation.messages.
The conversation was handed over to a person (status is now waiting).
A person answers this conversation: the message was saved, no assistant reply follows.
The turn is over.
The turn failed. The stream ends after this.
Events streamed while the assistant answers a message.