Fix METADAPT-A transaction IDs not starting at 1/-1

metadapta.go

@@ -37,6 +37,11 @@ func AdaptA(underlying net.Conn, party Party) Conn {
 		transChan:  make(chan *transA),
 		done:       make(chan struct { }),
 	}
+	if party == ClientSide {
+		conn.transID =  1
+	} else {
+		conn.transID = -1
+	}
 	go conn.receive()
 	return conn
 }
@@ -60,6 +65,7 @@ func (this *a) OpenTrans() (Trans, error) {
 	id := this.transID
 	this.transID ++
 	trans := &transA {
+		parent:   this,
 		id:       id,
 		incoming: usync.NewGate[incomingMessage](),
 	}

option.go

@@ -21,3 +21,10 @@ func (option Option[T]) Ok() bool {
 func (option Option[T]) Get() (T, bool) {
 	return (ucontainer.Optional[T])(option).Value()
 }
+
+func (option Option[T]) Default(defaul T) T {
+	if value, ok := option.Get(); ok {
+		return value
+	}
+	return defaul
+}