Agent Skills: ring:using-lib-systemplane

Using lib-systemplane, the hot-reload runtime-config plane (Postgres LISTEN/NOTIFY or MongoDB change streams), in two modes. Sweep Mode detects DIY config reload (SIGHUP, fsnotify, viper, pgx LISTEN), manual tenant-scoping, hand-built admin CRUD, and v4 residue. Reference Mode catalogs client lifecycle and migration-only provisioning. Go-only. Gated migration goes to ring:migrating-to-lib-systemplane. Skip for non-Go.