A machine the mesh could not read is not a machine that runs nothing

Three gatherers walk every node and pass over one whose plan will not
compose, so that one broken set does not cost the rest. They read a
plain error to mean that, and so read a store that was briefly
unreachable as a machine running nothing.

On the roster of routed names that is not a degraded answer but a false
one: it states to every machine at once that another machine's names do
not exist. Because the roster is part of every container's identity, a
control node replaced every container it ran — its own store, the
registry, the edge, mail, the bus — on a six-minute cycle for hours. The
loop closed through the store this is read from: each pass restarted it,
the read failed, one name left the roster, and the roster changing is
every container changing.

planFor now marks the two failures that really are the node's own — its
set not composing, and a setting that reaches nothing — and the three
gatherers pass over those and only those. Every other failure is raised,
naming the machine and the read, because a mesh-wide refusal with
nothing named in it is the other way to lose an evening.

novox/hq 04-ISSUES/152, and 151 for why a changed roster is a changed
container.

cmd/mesh-controller/network.go

@@ -346,9 +346,16 @@ func whoResolves(ctx context.Context, open *stores, requirement string) (
 	refused := map[string]string{}
 	for _, n := range nodes {
 		plan, _, err := planFor(ctx, open, n.Name)
-		if err != nil {
+		switch {
+		case unresolvable(err):
 			refused[n.Name] = err.Error()
 			continue
+		case err != nil:
+			// Not a node that does not resolve — a question that went unanswered. Recording it as a
+			// refusal would take the machine off the private network, and the generator that reads
+			// this would then write a roster and a filter without it (novox/hq 04-ISSUES/152).
+			return nil, nil, fmt.Errorf("whether %s answers %q cannot be read: %w",
+				n.Name, requirement, err)
 		}
 		for _, m := range plan.Modules {
 			for _, offered := range m.Offers() {