Node content now reads typed on every hub

A node type declares what its content is — Invitation, NotificationRule, GraphSubscriptionState and so on. That declaration configured the node's own hub and nothing else, so any other hub that read the node had no $type discriminator for the value and received an untyped JsonElement instead of the record.

That failure is completely silent. There is no exception and no error line: consumers written as content is Invitation simply see null, the view renders empty, and a reactive wait times out with nothing to point at.

It was found on memex.systemorph.com, where the portal logged at boot that Admin/_GraphSubscription/inbox "stayed an untyped JsonElement after deserialization". That node carries the state of the inbound-mail subscription, so the renewal could not see its own record and inbound mail on that install was dead — with every health signal green.

Seven built-in node types were in that position: EaCredential, GraphSubscriptionState, Invitation, MemexClientContent, NotificationChannel, NotificationRule and TeamsConversation. All seven now register their discriminator mesh-wide.

The lasting part is the guard. The two halves of this contract — the declaration, inside a hub configuration lambda, and the registration, a separate statement in the enclosing method — were joined by nothing, and omitting the second compiles, boots, serves and passes every test. A new governance test now reads both halves out of the source and fails when a node type declares a content type it never registers, naming the type and the three accepted spellings of the fix.