authority checks: bound the network phase, unconflate the metrics master
Follow-up to the 2026-08-13 authority stall (see relay docs/incidents/2026-08-13-zlay-authority-stall): checks wedged because the HTTP head phase had no deadline, and diagnosis was misdirected because relay_host_authority_network_time_us_total started its timer before pool acquisition — ~118s/check was mostly queueing behind the 4-slot resolver pool, not network. - bump zat v0.3.20 → v0.3.30: HttpTransport.head_deadline_ns (10s) bounds connect/TLS/send/receiveHead, so a peer that accepts and never answers can no longer pin a resolver slot indefinitely - network_time_us now starts after pool acquire; pool wait is its own counter, relay_host_authority_pool_wait_us_total Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>