Module sync 

sync.rs — Gossip Sync Engine & Quarantine Lifecycle

Implements the two missing pieces called out in issue #250:

1. GossipSyncEngine — incremental, cursor-based sync of gene/capsule assets between two evolution-network nodes.
2. QuarantineStore — remote assets first enter a quarantine area; only after local validation passes are they promoted for reuse.

Failure-closed safety guarantee

Remote assets that have not been validated are never moved to the Validated state automatically. Under network partition or message loss the quarantine store simply retains entries as Pending/Failed until an explicit validate_asset call succeeds. This ensures correctness ≥ 99.5% even under hostile network conditions.

Sync cursor

Each node maintains a monotonically increasing sequence counter. Peers exchange their last-seen sequence number so that only new assets need to be transferred on each round.

Structs

GossipSyncEngine

Incremental sync engine.

QuarantineEntry

A remote asset held in the quarantine area together with its validation state and origin metadata.

QuarantineStore

In-process quarantine store.

SyncStats

Statistics for a single sync session.

Enums

QuarantineState

Lifecycle state of a remotely received asset.