Sign template and fan it out to the relevant write/inbox relays.
Optionaloptions: OutboxPublishOptionsResolve relays, query them, dedup by id, validate signatures, collect events.
Optionaloptions: OutboxQueryOptionsReturn the relay plan the shell would use for a read/write target.
Open a live outbox-aware subscription, streaming through sink.
Abstract outbox router. Implementors own relay discovery (NIP-65 / NIP-66), routing, fallback, deduplication, signature validation, signing, and publish fanout. The service translates wire envelopes into these calls and back.