LlmRelayResolver typedef
LlmRelayResolver =
LlmRelayTarget? Function(LlmRelayRequest request)
Resolves the server-side target for one relay request (SEC-01).
Returns null → anonymous mode: the request's own baseUrl is honored
and NO stored key is ever attached. A non-null LlmRelayTarget is
either the record-backed endpoint+key pair or a named rejection.
Implementation
typedef LlmRelayResolver = LlmRelayTarget? Function(LlmRelayRequest request);