.NET code quality - enforcement, not opinion

The csharp skill says what good C# looks like; this skill makes a build prove it. The goal is that style and correctness rules are a gate the compiler and CI enforce, so they never depend on a reviewer noticing. Baseline is .NET 8 / C# 12. This is about configuring the tools - authoring your own Roslyn analyzers is dotnet-source-generators, and judging whether the tests are any good is dotnet-testing.

Two owners, one boundary: formatting vs rules

Split the space cleanly so two tools never fight over the same bytes:

• A formatter owns layout - whitespace, wrapping, brace placement. Pick CSharpier: it is opinionated and effectively zero-config, which ends the formatting debate instead of relocating it into .editorconfig knobs. The alternative, dotnet format, drives whitespace from .editorconfig style rules - fine if a repo has already standardized on it, but do not run both as formatters.
• .editorconfig + analyzers own rules - naming, usings, severity, the CA/IDE diagnostics. Formatting style rules effectively defer to the formatter.

Document which tool owns formatting once (in the repo's CLAUDE.md / AGENTS.md) so an agent never reformats under the wrong engine.

Install CSharpier as a local tool for reproducible local-and-CI runs, not globally: