fix: resolve pre-existing CI failures

[vivekkalyan]

Summary

• ruff format: src/art/cli.py and src/art/tinker/server.py
• ty type error in src/art/tinker/server.py:64: The prompt_tokens method had return type list[int] but apply_chat_template returns a union type (str | list[int] | list[str] | list[list[int]] | BatchEncoding). Wrapped the return value with cast(list[int], ...) since the function is always called with parameters that produce list[int] output.

[bradhilton]

thank you 🙏 sorry for leaving these ci issues on main 😬