mcpg-plugin-backend-nats

NATS backend plugin for mcpg. Provides tool dispatch over NATS request/reply (BackendPlugin for `kind: "nats"`) and resource-change subscription over NATS Core subjects (WatchStrategyPlugin for `kind: "nats_topic"`). The main mcpg binary depends on this crate at runtime via the plugin registry and carries no direct async-nats dependency.