mesh-issues: an open whose write may have landed never says nothing was opened, and a module must itself be registered

From the review: a taken key that cannot be read back, or a write never
confirmed, now tells the caller to get the number before opening again; an
owner entry naming a module is owned only by that module registered; link
targets get the secret guard; line separators are refused in one-line fields;
the acceptance test now proves the counter's own updates were contended.

modules/mesh-issues/cmd/mesh-issues/bus_test.go

@@ -43,9 +43,11 @@ func TestMain(m *testing.M) {
 type bus struct {
 	// lost counts the compare-and-sets another writer won: proof the openers collided.
 	lost atomic.Int64
-	nc   *nats.Conn
-	js   jetstream.JetStream
-	kvs  map[string]jetstream.KeyValue
+	// counterLost counts only the counter's updates another opener won: proof the counter itself was contended.
+	counterLost atomic.Int64
+	nc          *nats.Conn
+	js          jetstream.JetStream
+	kvs         map[string]jetstream.KeyValue
 }
 
 func newBus(t *testing.T) *bus {
@@ -243,6 +245,9 @@ func (i *instance) answer(m rpc) {
 			errors.As(err, &api) && api.ErrorCode == jetstream.JSErrCodeStreamWrongLastSequence {
 			code = -32010
 			i.b.lost.Add(1)
+			if m.Method == "mesh/state.update" && p.State == CountersState {
+				i.b.counterLost.Add(1)
+			}
 		}
 		i.say(map[string]any{"id": m.ID, "error": map[string]any{"code": code, "message": err.Error()}})
 		return
@@ -336,9 +341,10 @@ func TestFiftyOpensAtOnceFromTwoInstancesGetFiftyDistinctConsecutiveNumbers(t *t
 		}
 	}
 	// The openers collided: writes were refused because another opener had moved the counter first.
-	t.Logf("%d writes lost to another opener and tried again", b.lost.Load())
-	if b.lost.Load() == 0 {
-		t.Fatal("no opener ever lost a write: the test did not make them collide")
+	t.Logf("%d writes lost to another opener and tried again, %d of them the counter's updates", b.lost.Load(), b.counterLost.Load())
+	if b.counterLost.Load() < opens {
+		t.Fatalf("only %d of the counter's updates were lost to another opener: the test did not make the openers "+
+			"contend for the counter", b.counterLost.Load())
 	}
 	ctx := context.Background()
 	e, err := b.kvs[CountersState].Get(ctx, IssueCounter)