Stop wheel events bubbling out of the flags filter popup

PointerWheelChanged kept bubbling past the popup's ScrollViewer to the underlying
DataGrid, so spinning the wheel inside the dropdown also scrolled the grid behind.
Mark the event handled at the popup's root Border with handledEventsToo so the
inner ScrollViewer keeps its scroll behaviour but the event stops at the popup
boundary.

Assisted-by: Claude:claude-opus-4-7:Claude Code

ILSpy/Metadata/MetadataColumnBuilder.cs

@@ -174,24 +174,32 @@ namespace ILSpy.Metadata
 				MinHeight = 0,
 				VerticalAlignment = VerticalAlignment.Stretch,
 			};
+			var popupRoot = new Border {
+				BorderBrush = Brushes.Gray,
+				BorderThickness = new Thickness(1),
+				Background = Brushes.White,
+				// Force the arrow cursor on the popup surface — without this, the
+				// EW-resize cursor set on the DataGrid column header's drag-grip can
+				// leak into the popup if the pointer enters from there before
+				// Avalonia recomputes the cursor for the new hit-test target.
+				Cursor = new global::Avalonia.Input.Cursor(global::Avalonia.Input.StandardCursorType.Arrow),
+				Child = new ScrollViewer {
+					MaxHeight = 400,
+					Content = popupContent,
+				},
+			};
+			// Stop wheel events from bubbling out of the popup. Without this, scrolling
+			// inside the dropdown also scrolls the underlying DataGrid because the
+			// PointerWheelChanged event keeps bubbling up the routed-event tree once the
+			// inner ScrollViewer has consumed (or ignored) it.
+			popupRoot.AddHandler(global::Avalonia.Input.InputElement.PointerWheelChangedEvent,
+				(_, e) => e.Handled = true,
+				handledEventsToo: true);
 			var popup = new Popup {
 				PlacementTarget = openButton,
 				Placement = PlacementMode.BottomEdgeAlignedLeft,
 				IsLightDismissEnabled = true,
-				Child = new Border {
-					BorderBrush = Brushes.Gray,
-					BorderThickness = new Thickness(1),
-					Background = Brushes.White,
-					// Force the arrow cursor on the popup surface — without this, the
-					// EW-resize cursor set on the DataGrid column header's drag-grip can
-					// leak into the popup if the pointer enters from there before
-					// Avalonia recomputes the cursor for the new hit-test target.
-					Cursor = new global::Avalonia.Input.Cursor(global::Avalonia.Input.StandardCursorType.Arrow),
-					Child = new ScrollViewer {
-						MaxHeight = 400,
-						Content = popupContent,
-					},
-				},
+				Child = popupRoot,
 			};
 			openButton.Click += (_, _) => popup.IsOpen = true;
 			var row = new DockPanel { LastChildFill = true, Margin = new Thickness(0, 2, 0, 0) };