MeshTransportOptions.ModeClusterClient is gone. MeshTransportOptionsValidator accepts Dps or
Grpc and nothing else, so a node left carrying the string "ClusterClient" is now REFUSED at
boot naming MeshTransport:Mode and both remaining values — deliberately fail-closed rather
than falling back to Dps, which on a split-topology node would deliver nothing at all. A new
fact pins exactly that.
SplitTopologyTransportValidator tightens from an allow-list of two to Grpc only, as its own
comment said it would once ClusterClient was deleted. Dps on a cluster-role node stays
refused; the rule is still an explicit allow-list, so a typo'd mode fails too.
Tests: the two ClusterClient-mode facts in MeshTransportOptionsValidatorTests are deleted
(their Dps siblings already assert the same rule for the one remaining non-Grpc mode), the
SplitTopology fixtures move to Grpc, and the three-mode Theories in
ControlPlaneStarterOrderTests / CentralCommunicationActorTests become two-mode.
Joseph Doherty
af3b0c3146