Route network UI callbacks through UI queue

ui.go

@@ -37,6 +37,14 @@ func esc(str string) string {
 	return sanitize.HTML(clean)
 }
 
+// postUI is the only path network and audio callbacks use to touch terminal
+// widgets. Work is dropped during shutdown or queue overload.
+func (b *Barnard) postUI(fn func()) {
+	if b.Ui != nil {
+		b.Ui.Post(fn)
+	}
+}
+
 func (b *Barnard) Notify(event string, who string, what string) {
 	// Notifications are best-effort: a slow external command must not block a
 	// UI or network callback. New events are dropped once the bounded queue is full.