Modal for propose-approve and destructive confirms; the title sits over a double stationery rule.

```jsx
<Dialog
  open={open}
  onClose={close}
  title="Delete milestone"
  footer={<>
    <Button variant="ghost" onClick={close}>Keep it</Button>
    <Button variant="danger" onClick={confirm}>Yes, delete</Button>
  </>}
>
  This deletes the milestone and unhouses 12 issues. I'd like to hear you say yes.
</Dialog>
```

Body copy may be Reginald's (serif if quoted). Escape and scrim-click close it.
