Map protected-internal types to the plain protected overlay

The WPF frontend uses a type-only overlay mapper that shows protected
internal types with the plain protected badge, while members get the
combined protected-internal badge; the Avalonia frontend ran both through
the shared Images.GetOverlay and so badged types differently. Restore the
type-only mapping in TypeTreeNode.GetIcon, which now also covers search
results and every other caller of the helper.

Assisted-by: Claude:claude-fable-5:Claude Code

ILSpy.Tests/Search/SearchResultFactoryIconTests.cs

@@ -91,6 +91,20 @@ public class SearchResultFactoryIconTests
 		icon.BaseImage.Should().BeSameAs(Images.Enum);
 	}
 
+	[AvaloniaTest]
+	public void Protected_Internal_Nested_Type_Gets_Plain_Protected_Overlay()
+	{
+		var nested = fixtureType.NestedTypes
+			.Single(t => t.Name == "NestedProtectedInternal").GetDefinition()!;
+
+		var icon = (LayeredImage)factory.Create(nested).Image;
+
+		// Types map protected-internal to the plain protected badge; only members show
+		// the combined protected-internal badge. Matches the WPF frontend's type-only
+		// overlay mapping.
+		icon.Overlays.Should().Equal(Images.OverlayProtected);
+	}
+
 	[AvaloniaTest]
 	public void Location_Image_Reflects_Declaring_Type_Icon()
 	{
@@ -113,5 +127,7 @@ class SearchIconFixture
 	internal interface INested { }
 
 	enum NestedEnum { None }
+
+	protected internal class NestedProtectedInternal { }
 }
 #pragma warning restore CS0169

ILSpy/TreeNodes/TypeTreeNode.cs

@@ -75,8 +75,13 @@ namespace ICSharpCode.ILSpy.TreeNodes
 				TypeKind.Enum => Images.Enum,
 				_ => Images.Class,
 			};
-			return Images.GetIcon(baseImage,
+			// Types map protected-internal to the plain protected badge; only members show
-				Images.GetOverlay(type.Accessibility), type.IsStatic);
+			// the combined protected-internal badge. Matches the WPF frontend's type-only
+			// overlay mapping.
+			var overlay = type.Accessibility == Accessibility.ProtectedOrInternal
+				? AccessOverlayIcon.Protected
+				: Images.GetOverlay(type.Accessibility);
+			return Images.GetIcon(baseImage, overlay, type.IsStatic);
 		}
 
 		public override bool CanExpandRecursively => true;