Agent Skills: ring:using-lib-commons

Using lib-commons v5, Lerian's shared Go library (non-observability surface), in two modes. Sweep Mode detects DIY code replaceable by lib-commons at file:line. Reference Mode catalogs lifecycle (Launcher), outbox repo, circuit breakers, tenant management, idempotency, security/TLS, database, and HTTP toolkit. Observability moved to ring:using-lib-observability. Go-only. Skip for non-Go.