No build reaches a machine without a gate; a release plan walks what waits (hq ADR 0236)

A send carries the machine's whole declaration, so at the switch to roll the next send of
anything would have carried the old default's backlog, unjudged, to every machine. A gated
send now carries and judges everything waiting on its machine; every other send is refused
or leaves the machine; a release plan walks what waits one machine at a time, the control
node last, and one that fails holds the next until a person releases it.

cmd/mesh-controller/healers.go

@@ -614,6 +614,9 @@ func lastReportOf(ctx context.Context, inv *inventory.Inventory, node string) (i
 // planStale is why a plan's wait is superseded or finished, and the state closing it leaves it in; empty
 // when it is neither, which is not H2's to repair.
 func planStale(ctx context.Context, inv *inventory.Inventory, p inventory.Plan) (state, why string, err error) {
+	if p.Release != nil {
+		return "", "", nil // a release plan walks machines, and its own gate says when it is done (ADR 0236)
+	}
 	recent, err := inv.RecentPlans(ctx, 50)
 	if err != nil {
 		return "", "", err