fix: set explicitly safe dimensions for Steam Deck

dzgui/views/dialogs/wizard.py

@@ -439,7 +439,10 @@ class CompletionPage(ScrolledWizardPage):
 class Assistant(Gtk.Assistant):
     def __init__(self, is_deck: bool, XDG: "Xdg"):
         super().__init__()
-        if not is_deck:
+        if is_deck:
+            # NOTE: deemed to be "safe" dimensions that exclude taskbar size
+            self.set_default_size(1085, 670)
+        else:
             self.set_default_size(1500, 900)
 
         self.config_path = XDG.config