Per-cluster mesh Phase 1 groundwork. Once the meshes split (Phase 2) central
can no longer see a site node's appsettings, so the transport ports it must
dial have to live in a row central can read.
AkkaPort is non-nullable with a 4053 default — every node listens on a
remoting port, so 0 is never a truthful value and pre-existing rows must
migrate to something real. GrpcPort is nullable with no default: nothing
listens on it until Phase 5, and a non-null default would assert a port that
does not exist.
Both are documented as central's dial targets rather than the node's own
binding config; the duplication against Cluster:Port is reconciled in Task 4.
The new SchemaCompliance test is red until the migration lands (Task 2).
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty
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