Last Tab Open in TabView Windowing Sample Not Draggable

[karkarl]

Describe the bug

In #874 a fix is done so that when there is only 1 tab left, it disables the drag and reordering. This is not the ideal "northstar" UX, as ideally the entire the last tab should become a draggable area for TitleBar. More investigation is needed to see how to enable this behaviour.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Go to TabView -> TabViewWindowing Sample
2. Close all tabs so that there is only one tab left in the window

Expected behavior

Should be able to drag entire window dragging the last tab.

Actual behavior

Nothing happens, window stays still.

Version Info

• Xaml Controls Gallery - Downloaded from Store
  • If so, which version? (1.2.x -- Found on the Settings page of the app.)
• WinUI 3 Controls Gallery - Downloaded from Store
  • If so, which version? (1.3.x -- Found on the Settings page of the app.)
• App built locally from source
  • If so, which branch? (WinUI 3 versions are built off the winui3 branch)