Answer a panicking verb with an error, say flag errors in the answer, and leave refused logins out of D15

Read verbs now run in the serving process, where a panic would end every
call; refused logins are nobody's reconnect loop (review of hq issue 327).

cmd/mesh-controller/servingbus.go

@@ -1,7 +1,10 @@
 package main
 
 import (
+	"flag"
 	"fmt"
+	"io"
+	"os"
 	"sync/atomic"
 
 	"github.com/novox/mesh-controller/internal/broker"
@@ -36,3 +39,11 @@ func aBus() (*broker.JetStream, error) {
 	}
 	return js, nil
 }
+
+// usageTo sends a command's flag errors and usage to where its answer goes when that is not this process's
+// output: a verb answered in the serving controller says them in its answer, not in the controller's log.
+func usageTo(set *flag.FlagSet, w io.Writer) {
+	if w != os.Stdout {
+		set.SetOutput(w)
+	}
+}