One guarded handler slot for a bundle's event and heartbeat handlers, so a reload never races the consumer's loop

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

node-tools/internal/runtime/events_test.go

@@ -160,7 +160,7 @@ func TestALongRunningBundleThatExitsIsStartedAgain(t *testing.T) {
 func fmtSprintf(format string, args ...any) string { return fmt.Sprintf(format, args...) }
 func errorf(format string, args ...any) error      { return fmt.Errorf(format, args...) }
 
-// A bundle loaded again sets its heartbeat handler while the consumer's loop hands a word on: no data race (-race),
+// A bundle loaded again sets its event and heartbeat handlers while the consumer's loop hands a word or an event on: no data race (-race),
 // and the heartbeat is asked of the bus only while some bundle holds a handler.
 func TestAHeartbeatHandlerSetAgainWhileWordsAreHandedOnIsNotARace(t *testing.T) {
 	m := &moduleEvents{}
@@ -170,16 +170,23 @@ func TestAHeartbeatHandlerSetAgainWhileWordsAreHandedOnIsNotARace(t *testing.T)
 	if m.beatAsked() {
 		t.Fatal("a heartbeat is asked while no bundle gave a handler")
 	}
+	took := &deliverSlot{}
+	took.set(func(json.RawMessage) error { return nil })
+	m.delivers = []*deliverSlot{took}
 	var got atomic.Int32
 	done := make(chan struct{})
 	go func() {
 		defer close(done)
 		for i := 0; i < 200; i++ {
 			slot.set(func(json.RawMessage) { got.Add(1) })
+			took.set(func(json.RawMessage) error { got.Add(1); return nil })
 		}
 	}()
 	for i := 0; i < 200; i++ {
 		all.handBeat(m, bus.Beat{At: time.Now()})
+		if err := all.handOut("mod", m, bus.Envelope{Key: "a.b", Body: json.RawMessage(`{}`)}); err != nil {
+			t.Fatal(err)
+		}
 	}
 	<-done
 	if !m.beatAsked() {