Advise a recheck for an unanswered check on a ready or rejected delivery (issue 451)

That check answered once, so the build queue is the wrong place to look.
mesh-delivery names the delivery's state as data (held); the controller
reads it and never the words. A line without it keeps the advice of 438.

cmd/mesh-controller/plain_words_test.go

@@ -452,3 +452,49 @@ func TestAnUnansweredMergeChecksTimeIsSaidInLocalTime(t *testing.T) {
 		t.Fatalf("a pending check without its time reads %q", o.Explanation)
 	}
 }
+
+// **An unanswered merge check on a ready or rejected delivery is told to recheck it** (novox/hq issue 451):
+// mesh-delivery says such a line too (issue 441) and names the delivery's state as data, `held`. That check already
+// answered once, so the build queue is the wrong place to look; a recheck of the delivery, named by its id, asks the
+// check again. A line with no delivery held keeps the advice of issue 438, and so does a line from a mesh-delivery
+// that does not say `held` yet: the controller never guesses the state from the words.
+func TestAnUnansweredMergeCheckOnAReadyOrRejectedDeliveryOffersARecheck(t *testing.T) {
+	line := func(held string) stalledLine {
+		var l stalledLine
+		raw := `{"id":"novox/mesh-controller@c11222026a3b","number":212,"state":"unanswered",` +
+			`"waiting":["mesh/merge-gate pending since 2026-10-11T00:11:39Z"],"for":"1h1m0s","bound":"1h0m0s",` +
+			`"h2":"none: its delivery is ` + held + `, a state the operator moves — the operator's",` +
+			`"says":"novox/mesh-controller#212 is open on main, which requires the merge check, and its delivery is ` +
+			held + ` here, but on the forge its check has not answered: mesh/merge-gate pending since ` +
+			`2026-10-11T00:11:39Z. The pull request waits on that status and nothing asks it again. A recheck of the ` +
+			`delivery asks its check again, as does a new commit on its branch"`
+		if held != "" {
+			raw += `,"held":"` + held + `"`
+		}
+		if err := json.Unmarshal([]byte(raw+`}`), &l); err != nil {
+			t.Fatal(err)
+		}
+		return l
+	}
+	for _, held := range []string{"ready", "rejected"} {
+		o := stalledObservations([]stalledLine{line(held)})[0]
+		t.Logf("%s: %s\nneeds: %s", held, o.Explanation, o.Needs)
+		if !strings.Contains(o.Needs, "mesh-delivery.recheck") || !strings.Contains(o.Needs, "novox/mesh-controller@c11222026a3b") {
+			t.Fatalf("a %s delivery's unanswered check is not offered its recheck: %q", held, o.Needs)
+		}
+		if strings.Contains(o.Needs, "build queue") || strings.Contains(o.Needs, "mesh-controller.queue") {
+			t.Fatalf("a %s delivery's unanswered check, which answered once, is sent to the build queue: %q", held, o.Needs)
+		}
+		if !strings.Contains(o.Explanation, "Its delivery is "+held) {
+			t.Fatalf("a %s delivery's explanation does not say its state: %q", held, o.Explanation)
+		}
+		if len(o.Actions) != 0 {
+			t.Fatalf("it offers an action the controller is not granted: %+v", o.Actions)
+		}
+	}
+	// No delivery held, or a mesh-delivery that does not say: the advice of issue 438, and no recheck.
+	o := stalledObservations([]stalledLine{line("")})[0]
+	if !strings.Contains(o.Needs, "in the build queue: mesh-controller.queue") || strings.Contains(o.Needs, "recheck") {
+		t.Fatalf("a line with no delivery held says to %q", o.Needs)
+	}
+}