Add clarifying comment about DPI scale factor structure

Co-authored-by: emako <24737061+emako@users.noreply.github.com>

Author: Copilot

QuickLook/ViewerWindow.Actions.cs

@@ -109,6 +109,7 @@ internal void ToggleFullscreen()
             var screenBounds = screen.Bounds;
 
             // Get DPI scale factor for proper coordinate conversion
+            // scale.Horizontal and scale.Vertical contain the DPI scaling ratios (e.g., 1.5 for 150%)
             var scale = DisplayDeviceHelper.GetScaleFactorFromWindow(this);
 
             // Set to normal state first to allow manual positioning