Function build_continuation_packet 

pub(crate) fn build_continuation_packet(
    tail: &[u8],
    starts_mid_line: bool,
    state: Option<RunningState<'_>>,
) -> Option<String>

The packet for a transcript tail, or None when it holds no user message to continue from. state, when the agent has one, goes first: it covers what happened before the verbatim tail begins (§4.4: state first, tail last).