Grant the controller its work queues' cancelled sets (hq issue 269)

A cancel writes the ask's id into the seat's cancelled set before deleting
the ask, and a write is a publish to the bucket's subject, which the
controller was not granted: against a server holding exactly the
controller's composed list, every cancel timed out.

internal/broker/controller_buckets_test.go

@@ -0,0 +1,31 @@
+package broker
+
+import (
+	"slices"
+	"testing"
+)
+
+// **The controller may write every bucket it writes** (novox/hq to-be 45 §1, issue 269). Writing a
+// key is a publish to the bucket's own subject, which the management interface's grant does not
+// cover: the cancelled sets' writes timed out for want of this, and the controller's own buckets
+// would have.
+func TestTheControllerMayWriteEveryBucketItWrites(t *testing.T) {
+	p, err := PermissionsFor(Principal{Kind: KindController, PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []string{"$KV." + CallsBucket + ".>", "$KV." + HandActsBucket + ".>"}
+	for _, seat := range seatsTheControllerAsks {
+		if hasCancelledSet(seat) {
+			want = append(want, "$KV."+CancelledSetName(seat)+".>")
+		}
+	}
+	for _, subject := range want {
+		if !slices.Contains(p.Publish, subject) {
+			t.Errorf("the controller may not publish %s, so it cannot write that bucket", subject)
+		}
+	}
+	if slices.Contains(p.Publish, "$KV.>") {
+		t.Error("the controller may write any bucket, a module's state included")
+	}
+}