Test projects are working.

Vector3Visualizer/Vector3VisualizerUserControl.cs

@@ -0,0 +1,14 @@
+using Vector3VisualizerSource;
+using Microsoft.VisualStudio.Extensibility.UI;
+
+namespace Vector3Visualizer;
+
+internal sealed class Vector3VisualizerUserControl : RemoteUserControl
+{
+    public Vector3VisualizerUserControl(Vector3Model? dataContext) : base(dataContext)
+    {
+        Vector3Model = (Vector3Model?)DataContext;
+    }
+
+    public Vector3Model? Vector3Model { get; }
+}