Mac support and packaging

[lilacheden]

Several modifications for improved cross-platform support and external integration:

1. Mac compatibility: Allow running searchers on MPS and move Linux-dependent packages (deepspeed, vllm) to optional extras
2. Optional Java: Allow running non-BM25 searchers without Java installed (lazy import BM25 only when used)
3. Pip installable: Add setuptools configuration to allow installing the repo and importing its components externally

[wu-ming233]

Hello! Thank you for your interest and contribution to BrowseComp-Plus!

Generally the device compatibility and lazy imports look good to me. However, may I ask if the same installation instructions in README would still default to install linux-dependent / CUDA packages on a linux machine, given the changes in pyproject.toml? If not, what should we update in the the instructions?

Thanks!

[lilacheden]

@wu-ming233 - thanks for your response.

You are right, I updated the uv.lock and updated the readme to include updated instructions and to specifically mention which components require a gpu.