Add Codex public benchmark smoke runner

[yzs15]

Summary

• Add a Codex CLI backend for the eval runner, including isolated CODEX_HOME setup and usage JSONL capture.
• Add a scaffold-only public Terminal-Bench heterogeneous-dates workload with oracle/fixtures/context partition.
• Add container smoke harness scripts and pytest contract tests for runner, driver, and multi-agent Codex flows.

Test Plan

• go test -count=1 ./tests/eval
• go test -count=1 ./tools/eval/runner
• python3 -m pytest tools/eval/container_smoke -q
• bash -n tools/eval/container_smoke/run_csv_to_parquet_smoke.sh tools/eval/container_smoke/run_heterogeneous_dates_codex_agents.sh tools/eval/container_smoke/run_heterogeneous_dates_driver_autonomous_smoke.sh tools/eval/container_smoke/run_heterogeneous_dates_driver_mcp_smoke.sh