Evidence obsolescence and refresh VOI

The fixture-backed value_of_evidence_obsolescence_refresh method models evidence age, half-life, obsolescence risk, drift, refresh cadence, living review value, and model-refresh value.

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

Use voiage generate-config evidence-obsolescence-refresh to create a starting JSON payload, then run voiage calculate-evidence-obsolescence-refresh INPUT.json.