Modern Valkey client for OCaml 5 + Eio (RESP3-only)

Eio-native Valkey client targeting OCaml 5.3+ and Valkey 7.2+ (including Valkey 8.1 / 9 additions: SET IFEQ, DELIFEQ, hash field TTL). RESP3 only; no Lwt/Async/legacy fallback. Connection layer has auto-reconnect, byte-budget backpressure, circuit breaker, keepalive, TLS, and optional domain split so the parser can't stall socket I/O. Cluster router with quorum-based topology discovery, MOVED/ASK/CLUSTERDOWN/TRYAGAIN retry, periodic refresh, and Read_from-aware replica routing (incl. AZ affinity). Valkey Bundle module wrappers cover Search, JSON, and Bloom.