feat(client): adopt an asynchronous Tokio runtime for the client frontend

crates/irtt-app/src/signal.rs

@@ -1,10 +1,22 @@
+#[cfg(any(feature = "server", feature = "tui"))]
 use std::sync::{
     atomic::{AtomicBool, Ordering},
     Arc,
 };
 
+#[cfg(any(feature = "server", feature = "tui"))]
 pub fn install_signal_handler(shutdown_requested: Arc<AtomicBool>) -> Result<(), ctrlc::Error> {
     ctrlc::set_handler(move || {
         shutdown_requested.store(true, Ordering::Relaxed);
     })
 }
+
+/// Preserve ctrlc's SIGINT/SIGTERM policy while waking the async client.
+#[cfg(feature = "client")]
+pub fn install_async_signal_handler() -> Result<tokio::sync::watch::Receiver<bool>, ctrlc::Error> {
+    let (shutdown, receiver) = tokio::sync::watch::channel(false);
+    ctrlc::set_handler(move || {
+        shutdown.send_replace(true);
+    })?;
+    Ok(receiver)
+}