csharp-unity-conventions rule recommends C# 10/12 features that Unity 6 (C# 9) cannot compile #30

Why it matters

This rule is injected into the AI's context for C# work and tells it to use language features Unity 6 cannot compile. Every file the AI writes with these patterns fails to build, and it contradicts the project's own "must compile on Unity 6.x" standard.

Evidence

rules/csharp-unity-conventions.mdc:23-24:

- Use file-scoped namespaces to reduce nesting
- Prefer primary constructors for simple data types

Unity 6.x compiles C# 9. File-scoped namespaces are C# 10 and primary constructors for classes/structs are C# 12. Every snippet in the repo also uses block-scoped namespaces, so the rule contradicts the snippets.

Suggested approach

• Remove both lines; replace with "Unity 6 uses C# 9: do not use file-scoped namespaces, primary constructors, required members, raw string literals, or collection expressions".
• Add a CI grep guard for ^namespace .*;$ in .cs files and these phrases in rules/skills.

Done when

No rule or skill recommends C# features above C# 9, and CI guards against regressions.