Name the bus upgrade as the mesh call a person makes, and say a same-source rebuild needs no step (review of #173)

The condition and the plan named the verb in command-line form; the operator reaches it through the mesh
MCP server, so it is written as that call. A rebuild of the same source moves nothing (issue 280), which
the plan cannot know before the build, so its line says so.

cmd/mesh-controller/changeplan_test.go

@@ -61,7 +61,7 @@ func TestAChangePlanSaysWhatEachMachineReceives(t *testing.T) {
 	// Said before the merge (novox/hq issue 336): merging it holds every send to the bus's machine until a
 	// person runs the bus's step, and the verb that does.
 	for _, want := range []string{"merging this needs a person's bus upgrade", "nothing else is sent to anchor",
-		"`mesh-controller.bus upgrade --why … --reversible|--irreversible`", "photos waits for a person",
+		"mesh_call mesh-controller.bus", "the same as the one running there", "photos waits for a person",
 		"nats provides mesh-bus"} {
 		if !strings.Contains(text, want) {
 			t.Errorf("the steps do not say %q:\n%s", want, text)