Feature packages now reach these domains through interface types only:
ISession/SessionFace (identity + prompt/cancel/loadOlder + the useSession
snapshot source), ISessions, IWorkspaces, ILayout, IConversation, and the
existing SlashServiceContract now actually mounted on Context.slash. The
concrete services implement their face; wire-pump and assembly entry
points stay on the classes. The provide-channel materialization and
current-projection logic moves into SessionProvideChannel so the
production service and the client test runtime share one implementation.
The workspaces service consumes sessions through the narrow SessionsPort.