[ananthsub]

Summary

• resolve LongMT runtime cache defaults through Gym's configured cache_dir instead of /opt/Gym/.cache
• propagate the resolved COMET cache to Ray actors while preserving all existing environment-variable overrides
• document the defaults and add regression coverage for configured cache paths

Test plan

• Run resources_servers/longmt_eval/tests/test_app.py
• Run scoped pre-commit checks for the changed files