docs: add Write Tests and Run Validation critical rules (#31)

Author: CalvinAllen

CLAUDE.md

@@ -14,8 +14,10 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 6. **Working an issue** - Always create a new branch from an updated main branch
 7. **Check branch status before pushing** - Verify the remote tracking branch still exists. If a PR was merged/deleted, create a new branch from main instead
 8. **Microsoft coding guidelines** - Follow [Microsoft C# coding conventions](https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/coding-conventions) and [.NET library design guidelines](https://learn.microsoft.com/en-us/dotnet/standard/design-guidelines/)
-9. **No co-authors** - Do not add co-author information on commits or pull requests
-10. **No "generated by" statements** - Do not add generated-by statements on pull requests
+9. **Write tests** - All new/refactored code requires tests where applicable
+10. **Run validation before commits** - Run `dotnet build` and verify no errors before committing
+11. **No co-authors** - Do not add co-author information on commits or pull requests
+12. **No "generated by" statements** - Do not add generated-by statements on pull requests
 
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