feat(managed): implement thread-safe cancellation token

crates/irtt-client/src/managed/cancellation.rs

@@ -0,0 +1,43 @@
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    Arc,
+};
+
+#[derive(Debug, Clone, Default)]
+pub struct CancellationToken {
+    cancelled: Arc<AtomicBool>,
+}
+
+impl CancellationToken {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn cancel(&self) {
+        self.cancelled.store(true, Ordering::SeqCst);
+    }
+
+    pub fn is_cancelled(&self) -> bool {
+        self.cancelled.load(Ordering::SeqCst)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn token_starts_uncancelled() {
+        assert!(!CancellationToken::new().is_cancelled());
+    }
+
+    #[test]
+    fn cancel_is_visible_through_clones() {
+        let token = CancellationToken::new();
+        let clone = token.clone();
+
+        token.cancel();
+
+        assert!(clone.is_cancelled());
+    }
+}