Documents the exact hook point chosen for each of the 3 dead observability primitives (access log, request-duration histogram, tracer provider) and the 11 named business-health metrics, verified against the real current code rather than assumed — including a pre-existing SLA-run status data quality gap surfaced along the way (documented, not fixed here). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>