Make the second merge check pass: the gate's mesh has a chain of its own; the tests follow delivery 2's meaning (issues 1121, 1108, 1109)

The merge gate raises the snapshot's mesh in a throwaway store and now gives it a chain in memory, since the chain lives only on the bus. A module with no commit is carried by no send (a send is read from the commits on the assignments' keys), so the grants step flags only a module with a commit as newly assigned. The tests that sent a module with no build record one, the merge test waits for the merges' consumer before publishing and for the last look of a window before the next test, the pending test follows a chain that deletes nothing, and a wait's settling is a value of its key.

cmd/mesh-controller/pending_integration_test.go

@@ -542,23 +542,26 @@ func TestAPendingAssignmentNeverWaitsSilently(t *testing.T) {
 		t.Fatalf("a module registered meanwhile: %+v", p)
 	}
 
-	// Ended rows are deleted after KeptFor (review point 7); open ones never, nor one whose condition is
-	// still open (second review, bug B).
+	// Ended waits are not deleted, for the chain removes no key (ADR 0408 section 4): after KeptFor they are no longer listed, open
+	// ones never are left out, nor one whose condition is still open (second review, bug B).
 	if _, err := inv.RecordPending(ctx, inventory.PendingAssignment{Node: "anchor", Module: "lost", Build: "build-lost"}); err != nil {
 		t.Fatal(err)
 	}
-	said := settlePending(ctx, open, time.Now().Add(inventory.KeptFor+time.Hour))
-	rows, err := inv.Pending(ctx, time.Unix(0, 0))
+	later := time.Now().Add(inventory.KeptFor + time.Hour)
+	settlePending(ctx, open, later)
+	rows, err := inv.Pending(ctx, later.Add(-inventory.KeptFor))
 	if err != nil {
 		t.Fatal(err)
 	}
 	for _, r := range rows {
 		if !r.Open() && (r.Raised == nil || r.Cleared != nil) {
-			t.Fatalf("an ended pending assignment with no open condition outlived %s: %+v (%v)", inventory.KeptFor, r, said)
+			t.Fatalf("an ended pending assignment with no open condition is listed past %s: %+v", inventory.KeptFor, r)
 		}
 	}
-	if !strings.Contains(strings.Join(said, "\n"), "deleted 1 pending assignment(s)") {
-		t.Fatalf("the applied row was not deleted: %v", said)
+	for _, r := range rows {
+		if r.Module == "heard" {
+			t.Fatalf("an applied wait is listed past %s: %+v", inventory.KeptFor, r)
+		}
 	}
 }