block: vhd: Test that try_clone preserves backend dispatch

Verify that a cloned disk produces the same async I/O backend
as the original for both sync and io_uring paths.

Assisted-by: Claude:Opus-4.6
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

block/src/fixed_vhd_disk.rs

@@ -187,4 +187,21 @@ mod unit_tests {
         let disk = FixedVhdDisk::new(file, true).unwrap();
         assert_async_io(&disk, true);
     }
+
+    #[test]
+    fn try_clone_preserves_sync_dispatch() {
+        let file = make_vhd_file();
+        let disk = FixedVhdDisk::new(file, false).unwrap();
+        let cloned = disk.try_clone().unwrap();
+        assert_async_io_from_dyn(cloned.as_ref(), false);
+    }
+
+    #[cfg(feature = "io_uring")]
+    #[test]
+    fn try_clone_preserves_io_uring_dispatch() {
+        let file = make_vhd_file();
+        let disk = FixedVhdDisk::new(file, true).unwrap();
+        let cloned = disk.try_clone().unwrap();
+        assert_async_io_from_dyn(cloned.as_ref(), true);
+    }
 }