Port quantitative digest freshness gate

[yvette-carlisle]

Summary

• add Docker quantitative aggregate entrypoint with baseline-runner digest gating
• add artifact freshness materializer for quantitative product manifests
• add focused freshness tests and document reproducibility boundaries

Validation

• python3 -m py_compile scripts/materialize-quantitative-artifact-freshness.py
• bash -n scripts/real-world-quantitative-docker.sh scripts/real-world-docker.sh
• rustfmt --check apps/elf-eval/tests/real_world_job_benchmark/quantitative/freshness.rs
• git diff --check
• cargo test -p elf-eval --test real_world_job_benchmark quantitative -- --nocapture
• cargo make --list-all-steps | rg 'real-world-memory-quantitative-(docker|scoreboard)'