Malachi.Cluster.MetadataMachine (malachi v0.8.13)

A ra (Raft) state machine that replicates Malachi.Metadata.

ra's apply/3 delegates to the pure, deterministic Metadata.apply/2, exactly the contract the metadata machine was designed for, so the control-plane metadata becomes durable and Raft-replicated with no change to the business logic. One ra cluster backs one DS-RSM vnode; leadership of that cluster is the vnode's coordinator.

Determinism is what makes this safe: every replica applies the same command log and reaches the same Metadata state (the property the MetadataPropertyTest pins down).