Function answer_to 

pub fn answer_to(
    homes: &HarnessHomes,
    record: &LiveRuntimeRecord,
    message_id: &str,
) -> Option<String>

The runtime’s answer to the message message_id: the text of its last assistant message after the user message that carried that id, read from the session’s own transcript (a hosted runtime’s attach history can be empty; its harness’s transcript never is). None until it has answered.