Advertise health-aware peer cache ranking

agents/rap-node-agent/cmd/rap-node-agent/main.go

@@ -2980,6 +2980,7 @@ func heartbeatPayload(cfg config.Config, identity state.Identity, meshState *syn
 		payload.Metadata["mesh_peer_recovery_report"] = meshPeerRecoveryReport(meshState, observedAt)
 		payload.Metadata["mesh_peer_connection_intent_report"] = meshPeerConnectionIntentReport(meshState, observedAt)
 		payload.Metadata["mesh_peer_connection_manager_report"] = meshPeerConnectionManagerReport(meshState, observedAt)
+		payload.Capabilities["mesh_peer_cache_endpoint_health_ranking"] = true
 		payload.Metadata["mesh_rendezvous_lease_report"] = meshRendezvousLeaseReport(meshState, identity, observedAt)
 		payload.Metadata["mesh_route_path_decision_report"] = meshRoutePathDecisionReport(meshState, identity, observedAt)
 		payload.Metadata["mesh_route_generation_report"] = meshRouteGenerationReport(meshState, identity, observedAt)

agents/rap-node-agent/cmd/rap-node-agent/main_test.go

@@ -1302,6 +1302,9 @@ func TestHeartbeatPayloadIncludesPeerRecoveryReportWithoutAdvertisedEndpoint(t *
 	if payload.Capabilities["mesh_peer_connection_intent_planning"] != true {
 		t.Fatalf("connection intent capability missing: %+v", payload.Capabilities)
 	}
+	if payload.Capabilities["mesh_peer_cache_endpoint_health_ranking"] != true {
+		t.Fatalf("peer cache endpoint health capability missing: %+v", payload.Capabilities)
+	}
 	if _, ok := payload.Metadata["mesh_endpoint_report"]; ok {
 		t.Fatalf("endpoint report should not be emitted without advertised endpoint: %+v", payload.Metadata)
 	}

docs/architecture/DISTRIBUTED_FABRIC_NODE_PROTOCOL_PLAN.md

@@ -353,6 +353,9 @@ degraded-path feedback as VPN fabric-session dialing.
 Peer cache snapshots expose best-candidate score reasons, giving diagnostics a
 direct explanation for why a QUIC, WebSocket, relay, or fallback endpoint was
 chosen.
+Heartbeat capabilities now advertise that peer-cache endpoint ranking consumes
+health observations, allowing control plane and UI diagnostics to detect nodes
+running the health-aware peer selection path.
 
 Deliverables: