nats: say whether a user's grant is in force on the running server, not only written (hq issue 353)

nats_user_can read the user list on the machine. A list written is not a list the bus enforces until
the server reloads it: on 2026-10-09 the controller asked between the write and the reload's effect.
The answer now carries in_force — allowed in the file, and the server's config_load_time after the
file's write — with why when it is not, and anything not known is not in force.

modules/nats/cmd/nats-tools/tools_test.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
+	"fmt"
 	"strings"
 	"testing"
 	"time"
@@ -170,3 +172,39 @@ func TestClosedConnectionsArePerUserAndNameAndSayWhichWereDropped(t *testing.T)
 		t.Errorf("narrowed: %+v", got)
 	}
 }
+
+// novox/hq issue 353: a grant written to the user list is in force only once the server reloaded after the
+// write; anything not known is not in force.
+func TestAGrantIsInForceOnlyWhenTheServerReloadedAfterTheListWasWritten(t *testing.T) {
+	written, err := ParseWritten("2026-10-09 17:55:56.422211788 +0200\n")
+	if err != nil {
+		t.Fatal(err)
+	}
+	varz := func(at string) []byte { return []byte(`{"config_load_time":"` + at + `"}`) }
+	allowed := func() map[string]any { return map[string]any{"allowed": true} }
+	cases := []struct {
+		name   string
+		answer map[string]any
+		werr   error
+		varz   []byte
+		verr   error
+		want   bool
+		says   string
+	}{
+		{"reloaded after the write", allowed(), nil, varz("2026-10-09T15:56:05.1Z"), nil, true, ""},
+		{"reloaded before the write", allowed(), nil, varz("2026-10-09T15:55:56.4Z"), nil, false, "has not reloaded"},
+		{"not allowed in the file", map[string]any{"allowed": false}, nil, varz("2026-10-09T15:56:05Z"), nil, false, "does not allow"},
+		{"the write time unknown", allowed(), errors.New("no container"), varz("2026-10-09T15:56:05Z"), nil, false, "no container"},
+		{"the server unknown", allowed(), nil, nil, errors.New("refused"), false, "could not be read"},
+		{"a server that says no load time", allowed(), nil, []byte(`{}`), nil, false, "does not say"},
+	}
+	for _, c := range cases {
+		got := InForce(c.answer, written, c.werr, c.varz, c.verr)
+		if got["in_force"] != c.want || (c.says != "" && !strings.Contains(fmt.Sprint(got["why"]), c.says)) {
+			t.Errorf("%s: %v", c.name, got)
+		}
+	}
+	if _, err := ParseWritten("yesterday"); err == nil {
+		t.Error("a write time that is not one was read")
+	}
+}