dotnet-winui WinUI 3 / Windows App SDK development: project setup with and Windows 10 TFM, XAML patterns with compiled bindings ( ) and deferred loading ( ), MVVM with CommunityToolkit.Mvvm, MSIX and unpackaged deployment modes, Windows integration (lifecycle, notifications, widgets), UWP migration guidance, and common agent pitfalls. Version assumptions: .NET 8.0+ baseline. Windows App SDK 1.6+ (current stable). TFM . .NET 9 features explicitly marked. Scope boundary: This skill owns WinUI 3 project setup, XAML patterns, MVVM integration, packaging modes, Windows platform integration, and UW…