Agent Skills: ring:using-tracing

Using lib-observability/tracing for OTEL provider lifecycle, trace-context propagation across HTTP/gRPC/queues, span error/event recording, and PII redaction, in two modes. Sweep Mode detects raw OTEL setup, hand-rolled header propagation, manual span-attribute assembly, and DIY redaction. Reference Mode catalogs Telemetry, Redactor, and propagation/span helpers. Go-only. Skip for non-Go or frontend code.