Simplify shutdown with cancellation tokens (#601)

daemon/src/display/headless.rs

@@ -1,6 +1,6 @@
 use log::info;
 use tokio::sync::mpsc::Receiver;
-use tokio::sync::oneshot;
+use tokio_util::sync::CancellationToken;
 use tokio_util::task::TaskTracker;
 
 use crate::config;
@@ -9,7 +9,7 @@ use crate::display::DisplayState;
 pub fn update_ui(
     _task_tracker: &TaskTracker,
     _config: &config::Config,
-    _ui_shutdown_rx: oneshot::Receiver<()>,
+    _shutdown_token: CancellationToken,
     _ui_update_rx: Receiver<DisplayState>,
 ) {
     info!("Headless mode, not spawning UI.");