Add unity-csharpconsole (C# REPL) and unity-cli-plugin (AI agent plugin)

[niqibiao]

What's added

Debugging section

• CSharp Console — Interactive Roslyn-powered C# REPL for Unity Editor and Runtime. Persistent session state, private member access, remote Player execution via HybridCLR, and an extensible `[CommandAction]` command framework. Fits alongside REX Diagnostics and RuntimeCodeExecuter as a runtime expression evaluation / debugging tool.

Tools section

• unity-cli-plugin — AI coding agent plugin for Unity Editor supporting Claude Code and Codex CLI. 40+ commands for scene editing, components, assets, screenshots, and profiling; falls back to a full Roslyn C# REPL via unity-csharpconsole.

Both projects are open-source (Apache 2.0), actively maintained, and Unity 2022.3+ compatible.