Fetch the messages (conversation) in a chat. The newest page is returned first; messages within the page are oldest→newest. Use offset to page backwards through history — hasMore=true means older messages exist.

Each message carries: direction (inbound/outbound), type, text, mediaUri, delivery status, timestamp, sender, the replying agent (if any), a replyTo quote (if any), templateName (if sent from a template) and email metadata (EMAIL channel only).

This is a pure read — it does NOT mark the chat as seen.