Refactor RDP proxy handling and update related tests

agents/rap-node-agent/internal/vpnruntime/gateway_test.go

@@ -95,6 +95,30 @@ func TestGatewayRunClosesPacketTransportOnRuntimeError(t *testing.T) {
 	}
 }
 
+func TestGatewayNormalizeRejectsBackendPacketRelayFallback(t *testing.T) {
+	gateway := &Gateway{
+		API:             nil,
+		ClusterID:       "cluster-1",
+		VPNConnectionID: "vpn-1",
+	}
+
+	err := gateway.normalize()
+	if err == nil {
+		t.Fatal("normalize succeeded without a fabric packet transport")
+	}
+	if got, want := err.Error(), "fabric packet transport is required; backend packet relay fallback is disabled"; got != want {
+		t.Fatalf("normalize error = %q, want %q", got, want)
+	}
+}
+
+func TestGatewaySnapshotReportsIPv4EgressServiceAdapter(t *testing.T) {
+	gateway := &Gateway{Transport: &recordingGatewayTransport{}, VPNConnectionID: "vpn-1"}
+	snapshot := gateway.Snapshot()
+	if snapshot["service_role"] != "ipv4-egress" || snapshot["service_class"] != "vpn_packets" || snapshot["adapter_contract"] != "fabric_channel_to_ipv4_nat" {
+		t.Fatalf("unexpected gateway service snapshot: %#v", snapshot)
+	}
+}
+
 func TestGatewayUploadPrioritizesTCPControlPackets(t *testing.T) {
 	transport := &recordingGatewayTransport{}
 	gateway := &Gateway{Transport: transport, VPNConnectionID: "vpn-1"}