Ask an acknowledgement apart from an approval, change every kept ask by compare-and-set, and rehearse rather than drill (hq ADR 0259, review M1/L2/L3/L7)

- M1: a condition offering both kinds of answer is asked twice: its authorising answers about the
  condition, its acknowledging ones (Silence) apart, so an answer from a channel that only acknowledges
  never ends an approval.
- L2: the asked store creates once and changes only over the revision it read, deciding again on what it
  reads; a stale cancel no longer writes over an act.
- L3: every ask is kept before it is published, one whose publishing failed is marked unsent and asked
  again, and a cancel is kept before it is said. The terminal's test question is now `rehearse`, so it is
  not called what the glossary calls a drill; its two answers are both approve-level.
- L7: two deliveries of one warrant to two controllers at once act exactly once, on a real bus.
- Re-vendored onto mesh-sdk 76902998 (canonical digests): an option binds an asks.Act with each argument
  as arg.<name>.
- The lab's bus fixture composes verified-sender only where the lab says its machine is root-free
  (MESH_LAB_ASKS_ROOT_FREE=true).

internal/inventory/asks_lab_test.go

@@ -98,7 +98,13 @@ func TestTheAsksLabBus(t *testing.T) {
 			Emits: own.Emits, Serves: own.Serves}
 	}
 	records := broker.Records{Nodes: []string{labMachine}, Assigned: map[string][]broker.Declared{},
-		People: map[string][]string{}, Interchangeable: map[string]bool{}}
+		People: map[string][]string{}, Interchangeable: map[string]bool{}, RootFree: map[string]bool{}}
+	// Whether the lab's machine is root-free is the lab's to say (MESH_LAB_ASKS_ROOT_FREE=true): it has no
+	// node-engine to judge it. Unsaid, it is not, and no kind is composed with verified-sender — as a push
+	// composes on a machine that is not (novox/hq ADR 0259 §8).
+	if os.Getenv("MESH_LAB_ASKS_ROOT_FREE") == "true" {
+		records.RootFree[labMachine] = true
+	}
 	var buckets []broker.Bucket
 	var trafficSeats []broker.Seat
 	for _, m := range manifests {