Improve how winapp ui --help is interpreted by agents

Some agents interpret <Arguments> as required in our help docs which creates interesting issues. For example, an agent frequently attempts to screenshot an app by passing "window" as an argument 

<img width="1186" height="348" alt="Image" src="https://github.com/user-attachments/assets/96a20e2f-35ae-4297-9f27-2285af9d24a2" />