The credential wait's test stays under a second, and a failed watch says the re-read, not a restart (issue 1496)

Review of 3baeaec: TestAwaitCredential took 1.9 s, over the unit limit; it now
sets the watch's settle to 10 ms, writes at 20 ms and gives up at 100 ms (0.2 s).
The watch's journal line for a failure named a bundle and a restart; the
credential wait now says it is read again every 30 s instead.

node-tools/cmd/node-tools/main.go

@@ -171,7 +171,8 @@ func awaitCredential(file string, until time.Time, say func(string, ...any)) (bu
 		case changed <- struct{}{}:
 		default:
 		}
-	}, func(format string, args ...any) { say(format, args...) })
+	}, func(format string, args ...any) { say(format, args...) },
+		fmt.Sprintf("the credential is read again every %s instead", rereadEvery))
 	if werr != nil {
 		say("cannot watch %s (%v): it is read again every %s instead", file, werr, rereadEvery)
 	} else {

node-tools/cmd/node-tools/main_test.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/novox/mesh-tools/node-tools/internal/bus"
+	"github.com/novox/mesh-tools/node-tools/internal/runtime"
 )
 
 // A runtime started before its credential is on the machine waits for it, woken by the watch of its directory, and gives
@@ -18,7 +19,9 @@ import (
 func TestAwaitCredential(t *testing.T) {
 	const good = `{"url":"tls://bus.example:4222","module":"m"}`
 	rereadEvery = time.Hour // only the watch can wake the read in time
-	t.Cleanup(func() { rereadEvery = 30 * time.Second })
+	settle := runtime.Settle
+	runtime.Settle = 10 * time.Millisecond // a unit test stays well under a second
+	t.Cleanup(func() { rereadEvery, runtime.Settle = 30*time.Second, settle })
 	place := func(path, body string) {
 		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
 			t.Fatal(err)
@@ -34,7 +37,7 @@ func TestAwaitCredential(t *testing.T) {
 	for _, c := range []struct {
 		name   string
 		before string // written before the wait, "" none
-		later  string // written 200ms into the wait, "" none
+		later  string // written 20ms into the wait, "" none
 		deeper bool   // the file's directory is not there at the start
 		bound  time.Duration
 		want   string // "" a credential; else a word of the error
@@ -44,7 +47,7 @@ func TestAwaitCredential(t *testing.T) {
 		{name: "written during the wait", later: good, bound: 5 * time.Second, said: 2},
 		{name: "empty, then filled", before: " ", later: good, bound: 5 * time.Second, said: 2},
 		{name: "its directory made during the wait", later: good, deeper: true, bound: 5 * time.Second, said: 2},
-		{name: "never written", bound: 400 * time.Millisecond, want: "waited", said: 1},
+		{name: "never written", bound: 100 * time.Millisecond, want: "waited", said: 1},
 		{name: "no url", before: `{"module":"m"}`, bound: 5 * time.Second, want: "not a broker credential", said: 0},
 	} {
 		t.Run(c.name, func(t *testing.T) {
@@ -57,7 +60,7 @@ func TestAwaitCredential(t *testing.T) {
 				place(file, c.before)
 			}
 			if c.later != "" {
-				go func() { time.Sleep(200 * time.Millisecond); place(file, c.later) }()
+				go func() { time.Sleep(20 * time.Millisecond); place(file, c.later) }()
 			}
 			var said []string
 			began := time.Now()