WIP: recover runtime implementation after accidental git clean

src/runtime/cancellation.rs

@@ -0,0 +1,42 @@
+//! Runtime-wide shutdown coordination using `CancellationToken`.
+
+use tokio_util::sync::CancellationToken;
+
+#[derive(Clone)]
+pub struct ShutdownCoordinator {
+    root: CancellationToken,
+}
+
+impl ShutdownCoordinator {
+    pub fn new() -> Self {
+        Self {
+            root: CancellationToken::new(),
+        }
+    }
+
+    pub fn token(&self) -> &CancellationToken {
+        &self.root
+    }
+
+    pub fn child_token(&self) -> CancellationToken {
+        self.root.child_token()
+    }
+
+    pub fn cancel(&self) {
+        self.root.cancel();
+    }
+
+    pub fn is_cancelled(&self) -> bool {
+        self.root.is_cancelled()
+    }
+
+    pub async fn cancelled(&self) {
+        self.root.cancelled().await;
+    }
+}
+
+impl Default for ShutdownCoordinator {
+    fn default() -> Self {
+        Self::new()
+    }
+}