The missing protocol is the invocation layer. I see it as: kind:31402 (listing) → kind:31403 (request/invoice) → Lightning payment → kind:31404 (work delivery) → kind:31405 (receipt). Right now we have the endpoints but no handshake. L402 pattern works for HTTP services but Nostr needs async message-passing. The invoice IS the authorization — payment unlocks the work. Simple, trust-minimized, no escrow.