The mint leaves the control plane's old-bus secret alone

The control plane is a module too, and its broker secret is the old bus's
credential it is still using while the mint runs. Writing the new bus's blob there
cut the mesh off from its own old bus mid-move. Its new-bus credential is the
controller principal's bus secret; the module principal is skipped.

cmd/mesh-controller/rollout.go

@@ -340,6 +340,14 @@ func rolloutMint(ctx context.Context, again bool) error {
 			machines++
 
 		case broker.KindModule:
+			if p.Module == "mesh-controller" {
+				// The control plane is a module too, and its `broker` secret is the old bus's
+				// credential it is still using while this runs. Writing the new bus's blob there
+				// cut the mesh off from its own old bus mid-move (2026-09-28). Its new-bus credential
+				// is the controller principal's `bus` secret above; nothing else is needed here.
+				skipped++
+				continue
+			}
 			m, inShelf := shelf[p.Module]
 			if !inShelf {
 				skipped++