Say a walk's start or end when a person stops, closes, retries or releases it, and a hand stop as stopped

plans stop|close, plans retry and upgrade release-backlog kept a walk's start or end mark without saying it,
so the router would hold what the walk touched until its bound; each now runs on the bus as plans go does.
A hand stop keeps who stopped it, so its outcome is stopped, not failed (review 15, ADR 0308, issue 532).

cmd/mesh-controller/release.go

@@ -812,14 +812,19 @@ func backlogCommand(ctx context.Context, sub string, args []string) error {
 	}
 	defer open.Close()
 	if sub == "release-backlog" {
-		release, err := open.inventory.HoldPlans(ctx, true)
-		if err != nil {
+		// Said on the bus (novox/hq ADR 0308 decision 1): the release plan starts walking here, and its start is
+		// said by the verb that opens it.
+		var p *inventory.Plan
+		if err := sayingOnTheBus(ctx, open.inventory, func() error {
+			release, err := open.inventory.HoldPlans(ctx, true)
+			if err != nil {
+				return err
+			}
+			defer release()
+			why.record(ctx, "upgrade release-backlog", nil)
+			p, err = releaseBacklog(ctx, open, link.Caller())
 			return err
-		}
-		defer release()
-		why.record(ctx, "upgrade release-backlog", nil)
-		p, err := releaseBacklog(ctx, open, link.Caller())
-		if err != nil {
+		}); err != nil {
 			return err
 		}
 		if p == nil {