dotnet-version-upgrade Comprehensive guide for .NET version upgrade planning and execution. This skill consumes the structured output from [skill:dotnet-version-detection] (current TFM, SDK version, preview flags) and provides actionable upgrade guidance based on three defined upgrade lanes. Covers TFM migration, package updates, breaking change detection, deprecated API replacement, and test validation. Out of scope: TFM detection logic (owned by [skill:dotnet-version-detection]), multi-targeting project setup and polyfill strategies (see [skill:dotnet-multi-targeting]), cloud deployment con…