Z index issues with sidebar

### Describe the bug

@stephenkissock reported the base text and sidebar popouts overlap the header

<img width="597" height="407" alt="Image" src="https://github.com/user-attachments/assets/35606224-c3a3-4cc2-89c9-4740902895f9" />

### REDACTED relevant log output

```shell

```

### Steps to Reproduce

Using version  "@usace/groundwork": "^3.15.1",