Task O.4: GET /metrics (session-auth) returns the caller tenant's counters
(interactions by kind/status, outbound by status, AI jobs + cost, tickets,
meetings, inbox, audit-link count) via findScope + Prisma groupBy — no cross-tenant
totals — plus a global relay-lag section. smoke-observability proves the mandated
gate end to end: x-trace-id response header, event correlationId == request trace,
audit link in DB, /metrics counters. Slice-4 verification: 122 tests green, builds,
boundary clean, observability smoke + all prior smokes pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
