Say so when the day asked about is out of reach

cmd/mavend/system_reply_test.go

@@ -35,6 +35,27 @@ func TestReplySystemDateOffset(t *testing.T) {
 	}
 }
 
+// A day she cannot work out must not come back as today's date — that is the
+// same silent wrong answer #388 was about, one step further out.
+func TestReplySystemUnknownDayIsHonest(t *testing.T) {
+	now := time.Date(2026, 7, 30, 14, 5, 0, 0, time.UTC)
+	h := systemHandler(now)
+	for _, u := range []string{
+		"какое число в пятницу",
+		"какое число через неделю",
+		"какое число в понедельник",
+	} {
+		got := h.replySystem(context.Background(), router.Decision{Utterance: u})
+		if got != onlyNearDaysReply {
+			t.Errorf("replySystem(%q) = %q, want the honest reply", u, got)
+		}
+	}
+	// The days she does know must not be caught by the same guard.
+	if got := h.replySystem(context.Background(), router.Decision{Utterance: "какое число завтра"}); got == onlyNearDaysReply {
+		t.Error("завтра was treated as an unknown day")
+	}
+}
+
 // TestReplySystemClockCity — the clock arm must not answer local time for a
 // question about another city (Vikunja #388). Known cities get their own zone;
 // unknown places get an honest "local time only".