feat(ADM-018): completed feature

work/artifacts/F-029/documenter.md

@@ -0,0 +1,21 @@
+# Documenter — F-029 Observability: traces and business metrics
+
+## Summary
+Observability module provides Tracer/Meter abstractions with in-process no-op implementations, a /ops/metrics route for admin, and business metric instrumentation on the checkout path.
+
+## API
+
+| Route | Access | Result |
+|---|---|---|
+| GET /ops/metrics | admin | Returns metrics snapshot |
+
+## Interfaces
+- Tracer.startSpan(name)/trace(name, fn)
+- Meter.counter/histogram
+
+## Evidence
+- work/artifacts/F-029/architect.md
+- work/artifacts/F-029/implementer.md
+- work/artifacts/F-029/reviewer.json
+- work/artifacts/F-029/security.json
+- work/artifacts/F-029/qa.json