Fix: secondary monitor windows now handle DPI changes at runtime

Secondary 'show on all monitors' windows had no DpiChanged handler, causing
them to become incorrectly sized when monitor DPI changed at runtime (e.g.,
docking/undocking). The cached ctx.DpiScaleX/Y values also went stale,
corrupting cursor hole-punch coordinates.

This adds a DpiChanged event handler to each secondary window that updates
the cached DPI scale, repositions/resizes the window, and rebuilds the
frame geometry.

Author: shanselman

WindowsEdgeLight/MainWindow.xaml.cs

@@ -1147,6 +1147,19 @@ private MonitorWindowContext CreateMonitorWindow(Screen screen)
             }
         };
 
+        window.DpiChanged += (s, dpiArgs) =>
+        {
+            ctx.DpiScaleX = dpiArgs.NewDpi.DpiScaleX;
+            ctx.DpiScaleY = dpiArgs.NewDpi.DpiScaleY;
+
+            window.Left = screen.WorkingArea.X / ctx.DpiScaleX;
+            window.Top = screen.WorkingArea.Y / ctx.DpiScaleY;
+            window.Width = screen.WorkingArea.Width / ctx.DpiScaleX;
+            window.Height = screen.WorkingArea.Height / ctx.DpiScaleY;
+
+            UpdateMonitorGeometry(ctx);
+        };
+
         return ctx;
     }