v1.2.0

Control-plane release — the node protocol grows the pieces an application needs to run a real HUB/Node infrastructure on it (enrolment, node-initiated calls, domain-specific discovery), instead of only the "worker node" shape where the hub calls the node and the node merely heartbeats.

Fully backward-compatible (additive): every new wire field is omitted when empty and every new hook defaults to null, so existing peers and callers are unaffected.

Added

• Bidirectional RPC. request/response now flow in both directions. A node calls the hub with NodeRuntime.request(action, payload:), answered by the hub's new NodeGateway.onRequest — which receives the calling RegisteredNode, so the hub knows who is asking and can authorize on its principal. Registration is a precondition: a request from a connection that has not registered is rejected ("Not registered") without reaching the handler. The hub→node direction (NodeGateway.request) is unchanged. Previously the only node-initiated message was query, so an application needed a second channel back to the hub.
• Enrolment. NodeRegister and NodeRegistered carry a Map<String, dynamic> payload, and NodeGateway.onRegister vets registrations — returning the ack payload, or throwing a HubException to reject (the hub replies error, closes, and never registers the node). Node-side: NodeConfig.registerPayload / NodeConfig.onRegistered and NodeRuntime.registration. This is the seam for CA-style enrolment: submit a CSR, get a signed certificate back.
• Node-side in-band handshake. NodeConfig.onHandshake runs on the raw connection before registering — the counterpart of the hub's existing ConnectionAuthenticator, which had no node-side half — so a node can now answer a challenge/response or key-agreement exchange. Unconsumed frames are replayed to the control protocol.
• Application-defined discovery. NodeDescriptor.attributes (Map<String, dynamic>, may nest — unlike the flat string-only labels and metadata), NodeQuery.filter, and the NodeMatcher port, so an application owns query semantics the hub cannot know about (version ranges, nested service catalogues). NodeRegistry.discover takes a where predicate.
• NodeUpdate (t: "update") — a node revises its advertised descriptor without re-registering.
• Json.optObject for reading free-form JSON object fields.

Changed

• NodeGateway.codec and NodeRuntime.codec are now typed ConnectionCodec<NodeControlMessage> rather than the concrete MessageCodec, so an application can supply its own wire format (e.g. binary) without forking either endpoint. MessageCodec.standard() remains the default; source-compatible for existing callers.

Fixed

• In-flight RPCs no longer hang when a connection drops. NodeGateway and NodeRuntime now fail their pending calls with NodeUnavailableException on disconnect, goodbye and heartbeat timeout, instead of leaving callers to wait out their own timeout. NodeRuntime's pending discovery queries were leaked on disconnect and are now cleared too.

Full Changelog: v1.1.0...v1.2.0