C# Refactoring (behavior-preserving)

Safely refactors C#/.NET code without changing behavior. USE FOR any request to refactor, rename, move, extract, inline, merge, consolidate, deduplicate, split, or modernize C# code, including partial/generated declarations, wrappers, public APIs, serialization/reflection/configuration names, friend assemblies, conditional compilation, and multi-targeted projects. Also use when a request calls a feature, bug fix, package/framework upgrade, or public nullability change a refactor and the behavior-changing part must be separated or declined. DO NOT USE FOR ordinary feature or bug fixes not presented as refactoring; standalone upgrades after reclassification (use dotnet-upgrade); adding tests; or formatting-only work.