Function clear_last_session_snapshot 

pub(crate) fn clear_last_session_snapshot(store: &Store)

Consume the durable “last session” record after a fully successful restore (called only once window_create::handle_create_window’s final window read-back succeeds — see that call site’s comment for why not any earlier). Best-effort, same as save_last_session_snapshot: a failure to clear just means a future stray/misused restore call could replay this snapshot again, which client_windowids_empty’s server-side check (handle_create_window) already independently guards against — this is defense in depth, not the only thing preventing duplicates.