Address soundness hole in cycle prevention

tests/performance/memory.rs

@@ -14,7 +14,7 @@ async fn test_memory_usage_10000_nodes() {
     let before_build = memory_usage_hint();
 
     // Create 10,000 nodes
-    let tasks: Vec<_> = (0..10_000)
+    let mut tasks: Vec<_> = (0..10_000)
         .map(|i| dag.add_task(task_fn(move |_: ()| async move { i })))
         .collect();
 
@@ -34,8 +34,8 @@ async fn test_memory_usage_10000_nodes() {
     println!("Additional memory for execution: ~{} bytes", exec_memory);
 
     // Verify some results
-    assert_eq!(dag.get(&tasks[0]).unwrap(), 0);
-    assert_eq!(dag.get(&tasks[9999]).unwrap(), 9999);
+    assert_eq!(dag.get(tasks.swap_remove(9999)).unwrap(), 9999);
+    assert_eq!(dag.get(tasks.swap_remove(0)).unwrap(), 0);
 
     // Memory should be reasonable (< 100MB for 10k simple nodes)
     assert!(