feat: set process titles on env server and workers

[mikasenghaas]

Summary

• Adds setproctitle dependency and set_proc_title utility to process_utils.py
• Labels env server process as Verifiers::EnvServer and worker processes as Verifiers::EnvWorker{N}
• Makes verifiers processes identifiable in ps, htop, and pstree for easier debugging

Companion to PrimeIntellect-ai/prime-rl#2159 which sets titles on all prime-rl entrypoints.

🤖 Generated with Claude Code

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Note

Low Risk
Low risk: changes are limited to setting process titles and adding a small runtime dependency, with no impact on request handling or shutdown logic.

Overview
Adds the setproctitle dependency and a new set_proc_title helper in process_utils to standardize process naming as Verifiers::{name}.

The env server and each env worker now set their process titles at startup (e.g., Verifiers::EnvServer, Verifiers::EnvWorker{N}) to make spawned processes easier to identify in ps/htop/pstree.

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