Fix #338

This pull request introduces four new reference documents to the .claude/skills/code-review-netsync/references directory. These documents establish comprehensive code review guidelines for the repository, covering protocol change impact, Python server rules, Unity C# standards, and repo-wide practices. The addition provides clear checklists and best practices for reviewers and contributors, ensuring consistency, safety, and maintainability across the codebase.

Repository-wide standards and protocol impact:

• Added protocol-change-checklist.md outlining a detailed impact checklist for protocol changes, including serialization parity, test requirements, simulator updates, server and Unity client handling, and mandatory documentation updates. Includes a review output template for protocol changes and a quick reference for protocol constants.
• Added repo-wide-rules.md describing repository-wide code review rules, including ZeroMQ patterns, protocol details, backward compatibility, threading, performance, documentation, version management, git practices, CI/CD, and security.

Language-specific code review rules:

• Added python-server-rules.md detailing Python server code review requirements: strict type annotations, formatting and linting standards, import organization, exception handling, logging, naming conventions, dataclass usage, constants/enums, test structure, and Python version requirements. Includes a pre-commit checklist.
• Added unity-csharp-rules.md specifying Unity C# code review rules: null and thread safety, namespace conventions, private field naming, region organization, UnityEvent initialization, memory/GC optimization, inspector attributes, XML documentation, file structure, and .meta file handling.