CmdPal: Ensure IconBox uses an initialized scale (#45980)

## Summary of the Pull Request

This PR makes sure that IconBox is using valid scale to prevent
defaulting to 0 and using poorly resizes full-scale image:

<img width="81" height="79" alt="image"
src="https://github.com/user-attachments/assets/55bbb08f-6f78-4c19-b7a6-748176dee9c8"
/>
vs 
<img width="89" height="88" alt="image"
src="https://github.com/user-attachments/assets/2dc26863-88c0-4c47-8798-023611d571b5"
/>


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## PR Checklist

- [x] Closes: #45973

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/IconBox.cs

@@ -135,6 +135,8 @@ public partial class IconBox : ContentControl
             _lastScale = XamlRoot.RasterizationScale;
             XamlRoot.Changed += OnXamlRootChanged;
         }
+
+        Refresh();
     }
 
     private void OnUnloaded(object sender, RoutedEventArgs e)
@@ -149,10 +151,13 @@ public partial class IconBox : ContentControl
     {
         var newScale = sender.RasterizationScale;
         var changedLastTheme = _lastTheme != ActualTheme;
+        var changedScale = Math.Abs(newScale - _lastScale) > 0.01;
+
+        _lastScale = newScale;
         _lastTheme = ActualTheme;
-        if ((changedLastTheme || Math.Abs(newScale - _lastScale) > 0.01) && SourceKey is not null)
+
+        if ((changedLastTheme || changedScale) && SourceKey is not null)
         {
-            _lastScale = newScale;
             UpdateSourceKey(this, SourceKey);
         }
     }
@@ -257,7 +262,11 @@ public partial class IconBox : ContentControl
                 return;
             }
 
-            var eventArgs = new SourceRequestedEventArgs(sourceKey, iconBox._lastTheme, iconBox._lastScale);
+            var scale = iconBox._lastScale > 0
+                ? iconBox._lastScale
+                : (iconBox.XamlRoot?.RasterizationScale > 0 ? iconBox.XamlRoot.RasterizationScale : 1.0);
+
+            var eventArgs = new SourceRequestedEventArgs(sourceKey, iconBox._lastTheme, scale);
             await iconBoxSourceRequestedHandler.InvokeAsync(iconBox, eventArgs);
 
             // After the await: