breathe-apicall

The ApiCallCluster Cluster impl — breathe's PROTOCOL-API I/O boundary (Redis CONFIG SET, Kafka, NATS JetStream). The hands that apply a LimitLayout::ApiCall { endpoint, command } decision by reading/writing a live data-system parameter via a TYPED Rust client (the `redis` crate) — no shell, no CLI. Mirrors HostCluster; reuses the one BandProvider. Side effects abstracted behind the async ApiCallEnv trait (the typed-spec-triplet testability seam).