CmdPal: Move ListViewModel.TextToSuggest property update back to UI thread (#45878)

## Summary of the Pull Request

This PR marshals the setting of the property ListViewModel.TextToSuggest
in SetSelectedItem to the UI thread, so that the change notification is
raised on that thread as well.

Regressed in #45764 

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## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/ListViewModel.cs

@@ -567,8 +567,12 @@ public partial class ListViewModel : PageViewModel, IDisposable
                     WeakReferenceMessenger.Default.Send<HideDetailsMessage>();
                 }
 
-                TextToSuggest = item.TextToSuggest;
-                WeakReferenceMessenger.Default.Send<UpdateSuggestionMessage>(new(item.TextToSuggest));
+                var suggestion = item.TextToSuggest;
+                DoOnUiThread(() =>
+                {
+                    TextToSuggest = suggestion;
+                    WeakReferenceMessenger.Default.Send<UpdateSuggestionMessage>(new(suggestion));
+                });
             },
             ct);
     }