fix: struct list `show` outputs invalid sb3

```css
struct Foo {
    bar
}
list Foo baz;
onflag {
    show baz;
}
```

outputs invalid sb3. causes turbowarp scaffolding to output an error. Project in editor:

<img width="848" height="501" alt="Image" src="https://github.com/user-attachments/assets/0236c003-691e-45a8-8011-dbb9bdcc45a2" />

While turbowarp desktop can make *something* of it, turbowarp scaffolding can not. This is bad.