Let the controller say a bucket it deleted at its first start (issue 1943; for issue 1945, B13)

ADR 0539 clause 13 has the controller delete the plan-state buckets once and say each as its event.

go/catalogue/seats.go

@@ -118,7 +118,10 @@ var defaultSeats = append([]Seat{
 			"assignment-changed", "declared-config-changed", "predefined-changed",
 			// A builder's key not taken in because the artifact store does not hold an artifact it names (novox/hq
 			// issue 1937): the builder builds it again.
-			"artifacts-gone"},
+			"artifacts-gone",
+			// A bucket of a state this release deleted, deleted at the controller's first start (novox/hq ADR 0539
+			// clause 13): the merge window's, the silent sends' and the building plans' hold, each said once.
+			"bucket-deleted"},
 		Serves: ControllerVerbs},
 	// The store's first verbs (novox/hq ADR 0159): the smallest set that makes the store askable,
 	// served by whichever module holds the seat with tools of these names.

go/catalogue/verbs_r6_test.go

@@ -101,3 +101,15 @@ func TestTheDeliverySeatHasNoPlanVerbs(t *testing.T) {
 		t.Errorf("the gate of release 5 cannot hold the seat: %v", err)
 	}
 }
+
+// 1943 (for 1945/AC14): the controller's seat says a bucket it deleted at its first start as its event, bucket-deleted
+// (ADR 0539 clause 13).
+func TestTheControllerSaysABucketItDeleted(t *testing.T) {
+	seat, ok := SeatNamed(ControllerSeatName)
+	if !ok {
+		t.Fatal("no controller seat")
+	}
+	if !SeatSays(seat.Emits, "bucket-deleted") {
+		t.Errorf("the controller's seat does not emit bucket-deleted: %v", seat.Emits)
+	}
+}