Function register_session_resume_preflight_handler 

fn register_session_resume_preflight_handler(
    engine: &Arc<WshRpcEngine>,
    state: &AppState,
)

session:resume_preflight — read-only, mutates nothing, spawns nothing.

The pane calls this on mount so it can say whether the conversation it’s displaying will actually be continued, instead of the user finding out by typing and watching the transcript clear (crate::backend::resume_preflight’s module doc).