Raise a failed unit, the module's and the machine's (hq issue 315)

A module's failed unit now arrives among its resources and raises the
module's own condition, named by the unit. The machine's own failed
units, which no module places, are one warning for the machine listing
them, cleared when none is listed. Nothing a send moved is among them,
so the gate never holds a send on that finding. The statement's units
are kept with the machine's health (migration 0080) and node show says
them.

cmd/mesh-controller/module_health.go

@@ -92,7 +92,7 @@ func stateHealth(ctx context.Context, inv *inventory.Inventory, k *conditions.Ke
 		}
 	}
 	stored, err := inv.RecordHealth(ctx, inventory.NodeHealth{Node: node, Contract: h.Contract, SaidAt: h.At,
-		HeardAt: now, Resources: resources, Streaks: streaks, Network: network})
+		HeardAt: now, Resources: resources, Streaks: streaks, Network: network, Units: unitsKept(h.Units)})
 	if err != nil || !stored {
 		if err == nil {
 			healthRefused.Add(1)
@@ -103,6 +103,14 @@ func stateHealth(ctx context.Context, inv *inventory.Inventory, k *conditions.Ke
 		return nil
 	}
 	err = judgeModuleHealth(ctx, inv, k, node, unhealthy, streaks, now)
+	// And the machine's own failed units (issue 315): what no module places, one finding for the machine.
+	if uerr := judgeUnits(ctx, k, node, h.Units); uerr != nil {
+		if err == nil {
+			err = uerr
+		} else {
+			err = fmt.Errorf("%w; %v", err, uerr)
+		}
+	}
 	// And every machine's network, from every machine's newest statement (ADR 0241): a statement about one
 	// machine can hold another's finding, or release it.
 	if nerr := judgeNetworks(ctx, inv, k, now); nerr != nil {
@@ -235,6 +243,14 @@ func sayWaiters(ctx context.Context, k *conditions.Keeper, hold *holding, p cata
 func moduleUnhealthyObservation(module, node string, rs []inventory.ResourceHealth) conditions.Observation {
 	var words, said []string
 	for _, r := range rs {
+		if r.Kind == link.KindUnit {
+			// A failed unit is named by the unit, which is what a person looks for (issue 315); the
+			// resource that places it — a package, a file — is evidence.
+			words = append(words, fmt.Sprintf("its unit %s %s", r.Target, r.Reason))
+			said = append(said, fmt.Sprintf("%s (unit %s, placed by %s): %s, since %s", r.Target, r.Target, r.Resource,
+				orNotSaid(r.Reason), r.Since.UTC().Format("2006-01-02 15:04:05 MST")))
+			continue
+		}
 		words = append(words, fmt.Sprintf("its %s %s %s", r.Kind, r.Resource, reasonWords(r)))
 		said = append(said, fmt.Sprintf("%s (%s %s): %s, %d look(s) in a row, %d restart(s) counted, since %s",
 			r.Resource, r.Kind, r.Target, orNotSaid(r.Reason), r.Streak, r.Restarts,