New CLI and meta-package

[SamuelMarks]

Following the resounding interesting shown in my initial PR, here's a follow-up PR.

I've taken care not to edit any of your codebase—except the root pyproject.toml + README.md—to increase the chance of patch acceptance.

See that README.md for usage tips, and here are some example runs:

ls

$ python3 -m jax_llm_examples.cli ls        
- deepseek_r1_jax
- gpt_oss
- kimi_k2
- llama3
- llama4
- qwen3

run

$ python3 -m jax_llm_examples.cli run -n qwen3

---

More love needs to be given to the search-path syntax (see my TODO) and the meta package needs to do better work in discerning each package's dependencies; but it's a start (and it works).

[rdyro]

CLI for models is a really cool idea as is your implementation, but it unfortunately falls outside the scope of this project.

The focus here is a high-performance reference implementation more than a runner.