cs-code-stylelisted

# C# Code Style - Write code that compiles clean under `<TreatWarningsAsErrors>true</TreatWarningsAsErrors>` and strict null-checking (`<Nullable>enable</Nullable>`). - Use the very latest C# 14 language features. - Use the `init` and `required` modifiers when appropriate rather than constructor-based parameters. - Use the compiler-synthesized `field` keyword for backing fields rather than declaring them manually. - Declare extension methods/properties in C# 14 `extension(Receiver) { ... }` blocks grouped by receiver type, rather than classic `this`-parameter extension methods. - Choose the data structure type deliberately: class, struct, readonly struct, record class, record struct, readonly record struct, ref struct, or readonly ref struct. - Prefer `is` and `is not` over `==` and `!=` where applicable. - Name exception variables `ex` by default (catch clauses, `Assert.Throws` results, etc.).