Host the Network Descriptor and JWKS #74

Build the tool, or the feature in the service, that produces and hosts a network's two published documents. The Descriptor is a signed JSON document identifying a network — its domain, operator, revision, status, the protocol versions and schema packs it speaks, and where its federation discovery endpoint is. The JWKS carries the public keys a peer uses to verify that signature. Together they are how one network finds out who another is, before any admission or traffic. Published documents at fixed paths on the network's own domain, not APIs.

Doc: Federated protocol → Handshake, Network Descriptor contract.

Open: the doc picks neither a signature algorithm nor a canonical encoding. Both must be decided and fixed before the first signature is published.

Parent: #48