Function interpret_streaming_with_vfs_observer 

pub async fn interpret_streaming_with_vfs_observer<F>(
    input: &str,
    on_output: Rc<RefCell<F>>,
    vfs: Option<Arc<dyn Vfs>>,
    observer: ObserverCallback,
) -> InterpreterResult
where
    F: FnMut(String) + 'static,

Like interpret_streaming_with_vfs, but also emits a [logicaffeine_runtime::SchedSnapshot] to observer after each scheduler slice — the Studio’s Tasks/Channels strip subscribes here to show a concurrent program’s live task and channel state as it runs.