Replace dual message-channel + RPC setup with a single registerPluginProtocol
path, unified sdk.channels (register/request/event/broadcast), RPC keepalive
(__p2ns.ping/pong), and core request lifecycle on RPC open. Update
global.profile and example.plugin, admin Plugin RPC stats, docs, and
test:plugin-rpc. Breaking: upgrade all peers together; no legacy adapters.
Align P2NS with current Autopass, Hypercore, Hyperdrive, and Protomux behavior:
add plugin DB recovery for incompatible persisted HyperDB data, stop
unconditional spec rebuilds via fingerprinting, update SDK replication paths,
and align proxy invite channels with p2ns.core-* protocols without replicating
Autopass over the p2ns topic.