XamlTextViewCreationListener assumes views have IVsTextView

**Version Used**:  VS 18.5

**Steps to Reproduce**:

1. Open multi-diff view from git pending changes after changing a .xaml file

Roslyn throws here:

<img width="536" height="101" alt="Image" src="https://github.com/user-attachments/assets/dd4f4658-a2a7-4e29-99e6-ba9709e7f80b" />
 

