Keep the core over an older record instead of refusing the send (issue 201, review 90)

Refusing the whole send wedged a machine whose gate put back the
controller and whose put-back send was refused: every later automatic
send there was refused, retried each tick, and held up every other walk.

A send now composes the controller and the node-engine at the build the
machine was last sent when the mesh's record is older, and carries the
rest; nothing is refused or retried, and a plan whose own build is the
older one ends with its gate superseded. A sent build that failed its
gate is never kept, so the next send completes a put-back. The condition
names the two ways out and clears on any send that carries the record,
a person's push included.

cmd/mesh-controller/push.go

@@ -1027,6 +1027,9 @@ func (b overTheBus) declare(ctx context.Context, s readyNode, body []byte) (stri
 	if err != nil {
 		return "", err
 	}
+	// A send that carried the mesh's record of the controller and the node-engine — a person's push included —
+	// ends the condition of one kept over it (novox/hq issue 201).
+	settleCoreDowngrades(ctx, b.open.inventory, s.node, s.declared.Builds)
 	if len(s.declared.Bindings) > 0 {
 		// And where it bound each consumer of a provision that keeps its data (novox/hq ADR 0232):
 		// what the next resolution keeps it at. On the same outliving context as the send's record.