cba3b2e960
Health contract: a write response (per-node refusals included) is the server answering, so it restores Healthy and advances LastSuccessfulRead; a write with no reply (transport failure / timeout) writes Degraded with the stamp preserved; a caller-cancelled write touches nothing. A good keep-alive with no outage or dead subscription latched now clears a Degraded left by a failed read/write instead of only moving the stamp (a subscription-only driver otherwise stayed Degraded until its next re-initialise). All writes are generation-stamped. Refs #743 Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT