New Feature Request: Custom `claude` launcher via environment variables to support use-cases like claude-code-router or locally forked versions of claude code

[roykim98]

There only seems to be two options--claude code, or cursor. For Claude Code, there is no way to customize the executable used by claude-code-ui; it is just claude. While users can configure in their PATH where claude should point, it would be nice to retain the flexibility of having claude-code-ui handling multiple versions of claude.

A popular project is https://github.com/musistudio/claude-code-router, which lets you use claude code with alternative LLM providers not officially supported, such as a local running LLM.

Something like CLAUDE_CODE_UI_CLAUDE_SPAWN_ALIAS which can default to just claude as it is today would be a no-op for existing users but allow users who run LLMs locally to be able to configure the spawn alias to something like ccr code.

I think this change-set would be fairly small and isolated. I can open a draft PR to illustrate this capability