Federated and privacy-preserving VOI

The value_of_federated_privacy_preserving method aggregates site-local net-benefit summaries with optional deterministic privacy noise. It reports privacy-budget loss, aggregation error, disclosure-risk metadata, and each site’s leave-one-out contribution to the aggregate decision value.

When individual-level access is blocked, a synthetic site-summary matrix can be supplied as a recorded fallback. The current implementation is fixture-backed; licensed multi-site data, cross-language/Rust parity, and stable-promotion review remain explicit gates.