Replication and reproducibility VOI

The fixture-backed value_of_replication_reproducibility method models replication probability, reproducibility failure risk, audit cost, reanalysis value, credibility adjustment, and evidence downgrade.

Evidence-production data provenance, cross-language parity, and mature/stable governance approval remain required before promotion.

Use voiage generate-config replication-reproducibility to create a starting JSON payload, then run voiage calculate-replication-reproducibility INPUT.json.