dotnet-add-testing Add test infrastructure scaffolding to an existing .NET project. Creates test projects with xUnit, configures code coverage with coverlet, and sets up the conventional directory structure. Scope boundary: This skill provides test project scaffolding only. For in-depth testing patterns -- xUnit v3 features, integration testing with WebApplicationFactory, UI testing, snapshot testing, test quality metrics, and testing strategy guidance -- see [skill:dotnet-testing-strategy] and the related testing skills. Prerequisites: Run [skill:dotnet-version-detection] first to determine…