WinUI plugin enhancements and add MVVM Toolkit skill

.github/plugin/marketplace.json

@@ -643,8 +643,8 @@
     {
       "name": "winui3-development",
       "source": "winui3-development",
-      "description": "WinUI 3 and Windows App SDK development agent, instructions, and migration guide. Prevents common UWP API misuse and guides correct WinUI 3 patterns for desktop Windows apps.",
-      "version": "1.0.0"
+      "description": "End-to-end WinUI 3 and Windows App SDK toolkit: expert agent, coding instructions, UWP-to-WinUI 3 migration guide, MVVM Toolkit reference, plus CLIs for packaging/debugging (winapp) and Microsoft Store publishing (msstore). Covers the full write → package → publish lifecycle for desktop Windows apps and prevents common UWP API misuse.",
+      "version": "1.2.0"
     }
   ]
 }

docs/README.instructions.md

@@ -61,6 +61,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-instructions) for guidelines on
 | [ColdFusion Coding Standards](../instructions/coldfusion-cfm.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcoldfusion-cfm.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcoldfusion-cfm.instructions.md) | ColdFusion cfm files and application patterns |
 | [ColdFusion Coding Standards for CFC Files](../instructions/coldfusion-cfc.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcoldfusion-cfc.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcoldfusion-cfc.instructions.md) | ColdFusion Coding Standards for CFC component and application patterns |
 | [CommonMark Markdown](../instructions/markdown.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fmarkdown.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fmarkdown.instructions.md) | Markdown formatting aligned to the CommonMark specification (0.31.2) |
+| [CommunityToolkit.Mvvm (MVVM Toolkit)](../instructions/mvvm-toolkit.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fmvvm-toolkit.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fmvvm-toolkit.instructions.md) | CommunityToolkit.Mvvm (MVVM Toolkit) coding conventions for ViewModels, commands, messaging, validation, and DI across WPF, WinUI 3, .NET MAUI, Uno Platform, and Avalonia. |
 | [Comprehensive Guide: Converting Spring Boot Cassandra Applications to use Azure Cosmos DB with Spring Data Cosmos (spring-data-cosmos)](../instructions/convert-cassandra-to-spring-data-cosmos.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fconvert-cassandra-to-spring-data-cosmos.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fconvert-cassandra-to-spring-data-cosmos.instructions.md) | Step-by-step guide for converting Spring Boot Cassandra applications to use Azure Cosmos DB with Spring Data Cosmos |
 | [Containerization & Docker Best Practices](../instructions/containerization-docker-best-practices.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcontainerization-docker-best-practices.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcontainerization-docker-best-practices.instructions.md) | Comprehensive best practices for creating optimized, secure, and efficient Docker images and managing containers. Covers multi-stage builds, image layer optimization, security scanning, and runtime best practices. |
 | [Context Engineering](../instructions/context-engineering.instructions.md)<br />[![Install in VS Code](https://img.shields.io/badge/VS_Code-Install-0098FF?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcontext-engineering.instructions.md)<br />[![Install in VS Code Insiders](https://img.shields.io/badge/VS_Code_Insiders-Install-24bfa5?style=flat-square&logo=visualstudiocode&logoColor=white)](https://aka.ms/awesome-copilot/install/instructions?url=vscode-insiders%3Achat-instructions%2Finstall%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2Fgithub%2Fawesome-copilot%2Fmain%2Finstructions%2Fcontext-engineering.instructions.md) | Guidelines for structuring code and projects to maximize GitHub Copilot effectiveness through better context management |

docs/README.plugins.md

@@ -92,4 +92,4 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-plugins) for guidelines on how t
 | [testing-automation](../plugins/testing-automation/README.md) | Comprehensive collection for writing tests, test automation, and test-driven development including unit tests, integration tests, and end-to-end testing strategies. | 9 items | testing, tdd, automation, unit-tests, integration, playwright, jest, nunit |
 | [typescript-mcp-development](../plugins/typescript-mcp-development/README.md) | Complete toolkit for building Model Context Protocol (MCP) servers in TypeScript/Node.js using the official SDK. Includes instructions for best practices, a prompt for generating servers, and an expert chat mode for guidance. | 2 items | typescript, mcp, model-context-protocol, nodejs, server-development |
 | [typespec-m365-copilot](../plugins/typespec-m365-copilot/README.md) | Comprehensive collection of prompts, instructions, and resources for building declarative agents and API plugins using TypeSpec for Microsoft 365 Copilot extensibility. | 3 items | typespec, m365-copilot, declarative-agents, api-plugins, agent-development, microsoft-365 |
-| [winui3-development](../plugins/winui3-development/README.md) | WinUI 3 and Windows App SDK development agent, instructions, and migration guide. Prevents common UWP API misuse and guides correct WinUI 3 patterns for desktop Windows apps. | 2 items | winui, winui3, windows-app-sdk, xaml, desktop, windows |
+| [winui3-development](../plugins/winui3-development/README.md) | End-to-end WinUI 3 and Windows App SDK toolkit: expert agent, coding instructions, UWP-to-WinUI 3 migration guide, MVVM Toolkit reference, plus CLIs for packaging/debugging (winapp) and Microsoft Store publishing (msstore). Covers the full write → package → publish lifecycle for desktop Windows apps and prevents common UWP API misuse. | 7 items | winui, winui3, windows-app-sdk, xaml, desktop, windows, mvvm, msix, microsoft-store |

docs/README.skills.md

@@ -236,6 +236,9 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [model-recommendation](../skills/model-recommendation/SKILL.md)<br />`gh skills install github/awesome-copilot model-recommendation` | Analyze chatmode or prompt files and recommend optimal AI models based on task complexity, required capabilities, and cost-efficiency | None |
 | [msstore-cli](../skills/msstore-cli/SKILL.md)<br />`gh skills install github/awesome-copilot msstore-cli` | Microsoft Store Developer CLI (msstore) for publishing Windows applications to the Microsoft Store. Use when asked to configure Store credentials, list Store apps, check submission status, publish submissions, manage package flights, set up CI/CD for Store publishing, or integrate with Partner Center. Supports Windows App SDK/WinUI, UWP, .NET MAUI, Flutter, Electron, React Native, and PWA applications. | None |
 | [multi-stage-dockerfile](../skills/multi-stage-dockerfile/SKILL.md)<br />`gh skills install github/awesome-copilot multi-stage-dockerfile` | Create optimized multi-stage Dockerfiles for any language or framework | None |
+| [mvvm-toolkit](../skills/mvvm-toolkit/SKILL.md)<br />`gh skills install github/awesome-copilot mvvm-toolkit` | CommunityToolkit.Mvvm (the MVVM Toolkit) core: source generators ([ObservableProperty], [RelayCommand], [NotifyPropertyChangedFor], [NotifyCanExecuteChangedFor], [NotifyDataErrorInfo]), base classes (ObservableObject / ObservableValidator / ObservableRecipient), commands (RelayCommand / AsyncRelayCommand), and validation. Companion skills: mvvm-toolkit-messenger for pub/sub, mvvm-toolkit-di for Microsoft.Extensions.DependencyInjection wiring. Works across WPF, WinUI 3, MAUI, Uno, and Avalonia. | `references/end-to-end-walkthrough.md`<br />`references/relaycommand-cookbook.md`<br />`references/source-generators.md`<br />`references/troubleshooting.md`<br />`references/validation.md` |
+| [mvvm-toolkit-di](../skills/mvvm-toolkit-di/SKILL.md)<br />`gh skills install github/awesome-copilot mvvm-toolkit-di` | Wire CommunityToolkit.Mvvm ViewModels into Microsoft.Extensions.DependencyInjection. Covers the .NET Generic Host composition root, constructor injection, service lifetimes (Singleton / Transient / Scoped), IMessenger registration, resolving ViewModels in Views, keyed services, testing seams, and the legacy Ioc.Default escape hatch. Use across WPF, WinUI 3, .NET MAUI, Uno, and Avalonia. | `references/dependency-injection.md` |
+| [mvvm-toolkit-messenger](../skills/mvvm-toolkit-messenger/SKILL.md)<br />`gh skills install github/awesome-copilot mvvm-toolkit-messenger` | CommunityToolkit.Mvvm Messenger pub/sub for decoupled communication between ViewModels (or any objects). Covers WeakReferenceMessenger vs StrongReferenceMessenger, IRecipient<TMessage>, RequestMessage<T> / AsyncRequestMessage<T> / CollectionRequestMessage<T>, ValueChangedMessage<T>, channels (tokens), and the ObservableRecipient activation lifecycle. Use across WPF, WinUI 3, .NET MAUI, Uno, and Avalonia. | `references/messenger-patterns.md` |
 | [my-issues](../skills/my-issues/SKILL.md)<br />`gh skills install github/awesome-copilot my-issues` | List my issues in the current repository | None |
 | [my-pull-requests](../skills/my-pull-requests/SKILL.md)<br />`gh skills install github/awesome-copilot my-pull-requests` | List my pull requests in the current repository | None |
 | [nano-banana-pro-openrouter](../skills/nano-banana-pro-openrouter/SKILL.md)<br />`gh skills install github/awesome-copilot nano-banana-pro-openrouter` | Generate or edit images via OpenRouter with the Gemini 3 Pro Image model. Use for prompt-only image generation, image edits, and multi-image compositing; supports 1K/2K/4K output. | `assets/SYSTEM_TEMPLATE`<br />`scripts/generate_image.py` |