fix(vllm): add ray to vllm extras (#3688)

[kvr06-ai]

Summary

lm_eval/models/vllm_causallms.py imports ray at module level (line 14), but ray is missing from the [vllm] extras in pyproject.toml. vllm itself does not pull ray in transitively (absent from vllm/requirements/cuda.txt and from vllm's PyPI requires_dist), so pip install lm_eval[vllm] currently produces an environment that fails on ImportError: No module named 'ray' the moment the backend loads.

Fixes #3688

Changes

• pyproject.toml: add "ray" to the vllm extras entry

Testing

• pip install -e '.[vllm]' now pulls ray, and python -c "import lm_eval.models.vllm_causallms" succeeds in a clean environment

Notes

The three ray call sites (@ray.remote, ray.get, ray.shutdown) sit inside the data_parallel_size > 1 and not self.V1 branch, so ray is technically only needed for multi-GPU data-parallel runs. A follow-up could lazy-import ray if the added install footprint becomes a concern, but that is out of scope for this fix. This PR keeps the existing import contract and only corrects the packaging metadata to match it.

[kvr06-ai]

@baberabb Would you mind taking a look when you get a chance? One-line metadata fix for #3688 (ray missing from [vllm] extras).

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