Function unread 

pub fn unread(
    home: &Path,
    msgs: &[Message],
    here: &str,
    session: &str,
    started: i64,
    now: i64,
) -> usize

How many of msgs (as read gives them) are for session of this node here (started at started) and not shown to it yet: what its next prompts or tool calls would show.