an act with nothing on the other end says so (V-556)

askClarify parked "Что сделать?" whatever was on the other end. With an empty
allowlist that question has no answer: she asks, fails, asks again and gives up,
three turns spent on a request she could have declined in the first one.

Empty allowlist now names the gap and parks nothing. A non-empty one still asks,
and names what she can run, capped at six, so the question is answerable.

cmd/mavend/clarify.go

@@ -156,6 +156,20 @@ func (h *reactiveHandler) askClarify(ctx context.Context, dec router.Decision) (
 	if !ok {
 		return "", false
 	}
+	// An act is the one gap that may have nothing on the other end. Ask only
+	// when she has something to run, and say what it is (Vikunja #556).
+	if slot == dialogue.SlotFn {
+		var allow []string
+		if h.matcher != nil {
+			allow = h.matcher.Allowlist()
+		}
+		reply, ask := fnClarify(allow, 1)
+		if !ask {
+			log.Printf("voice: clarify — act with %d allowlisted fns; naming the gap instead of asking", len(allow))
+			return reply, reply != ""
+		}
+		question = reply
+	}
 	h.clarifyStore.Put(dialogueIDOf(ctx), &dialogue.PendingQuestion{
 		Intent:      dialogue.Intent(dec.Intent),
 		Slots:       toDialogueSlots(dec.Slots),