Lighter column-header hover, arrow cursor in filter popup

Two readability fixes for the metadata grid:
- Override DataGridColumnHeaderHoveredBackgroundBrush / Pressed to the toolbar accent
  palette so the Simple theme's saturated dark fill stops burying header text while
  sorting / resizing.
- Force StandardCursorType.Arrow on the filter popup's root Border. Without it the
  EW-resize cursor set by the column header's drag-grip can leak into the popup if
  the pointer enters from there before Avalonia recomputes the cursor.

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

ILSpy/App.axaml

@@ -26,6 +26,13 @@
         <!-- Suppress the gray pointer-over highlight on rows and cells. -->
         <SolidColorBrush x:Key="DataGridRowHoveredBackgroundBrush" Color="Transparent" />
         <SolidColorBrush x:Key="DataGridCellHoveredBackgroundBrush" Color="Transparent" />
+
+        <!-- Replace the Simple theme's saturated dark fill on column-header hover/press
+             with the toolbar accent palette (#330078D7 hover, #660078D7 pressed). The
+             default makes header text unreadable while sorting / resizing; the lighter
+             translucent accent matches MainToolBar.axaml's button hover treatment. -->
+        <SolidColorBrush x:Key="DataGridColumnHeaderHoveredBackgroundBrush" Color="#330078D7" />
+        <SolidColorBrush x:Key="DataGridColumnHeaderPressedBackgroundBrush" Color="#660078D7" />
     </Application.Resources>
 
     <Application.DataTemplates>

ILSpy/Metadata/MetadataColumnBuilder.cs

@@ -182,6 +182,11 @@ namespace ILSpy.Metadata
 					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,