Node: speak OpenVibe.Bot's real device protocol (plan T15 follow-up B) (#2)

ddiff --git a/internal/node/node.go b/internal/node/node.go
iindex 2ed526b..3bce9ae 100644
---- a/internal/node/node.go
++++ b/internal/node/node.go
@@@ -76,7 +76,8 @@ type Node struct {
  	// configured is set by the first config on a connection; until then only halt runs, so a latch the owner set
  	// while the link was down is applied before any motion.
  	configured bool
--	robotIDs   []string // from this connection's hello
++
++	robotIDs []string // the robots this device serves, from the connection's hello
  }
  
  // New builds a Node. Run starts it.
@@@ -443,19 +444,18 @@ func (n *Node) pollLatch(ctx context.Context) {
  
  // sendEstopState reports the device's latch. Bot reads latched:true as "this device is stopped" and latches the robot
  // (so the local kill switch shows on the panel and the gate stops sending motion); latched:false is a report only
--// and never clears the owner's latch.
++// and never clears the owner's latch. robot_id names the robot when the device serves exactly one.
  func (n *Node) sendEstopState() {
  	if !n.reporting() {
  		return
  	}
--	st := n.latch.State()
--	// robot_id names the robot only when the device serves exactly one; a bridge for several leaves it out.
--	var robot string
  	n.mu.Lock()
++	var robot string
  	if len(n.robotIDs) == 1 {
  		robot = n.robotIDs[0]
  	}
  	n.mu.Unlock()
++	st := n.latch.State()
  	n.send(protocol.EstopState{Latched: st.Stopped(), By: "device", At: time.Now().UTC().Format(time.RFC3339Nano),
  		RobotID: robot, LocalStop: st.Local, Reason: st.RemoteReason})
  }
ddiff --git a/internal/node/node_test.go b/internal/node/node_test.go
iindex f6ee8e2..7023dc2 100644
---- a/internal/node/node_test.go
++++ b/internal/node/node_test.go
@@@ -227,8 +227,8 @@ func TestPairConnectAndStatus(t *testing.T) {
  	for _, f := range e.conn.Frames() {
  		if f.Type == protocol.TypeEstopState {
  			sawEstopState = true
--			if f.Msg.(protocol.EstopState).Latched {
--				t.Fatal("latched on a fresh device")
++			if m := f.Msg.(protocol.EstopState); m.Latched || m.RobotID != fakebot.RobotID {
++				t.Fatalf("estop_state on a fresh device: %+v", m)
  			}
  			if r := f.Msg.(protocol.EstopState).RobotID; r != fakebot.RobotID {
  				t.Fatalf("estop_state robot_id %q on a one-robot device", r)