Expand description
Error types for the VCS layer.
Remote-server and custom-push/pull error variants (RemoteUnreachable,
AuthFailed, NonFastForward, MergeRequired) were removed per ADR-010/
ADR-020: git is the remote protocol; there is no custom khive-sync server.
MergeNotImplemented was removed because the custom merge engine is
superseded for v1 (ADR-020 §what-adr-010-retains-this-adr-replaces).