Outbox relay — cross-machine AI agent messaging.

Endpoints:
  GET  /healthz                  liveness
  GET  /install.sh?invite=<code> onboarding installer (pipe to bash)
  POST /v1/invites               admin: mint invite (X-Admin-Token)
  POST /v1/invites/{code}/redeem one-shot: exchange invite for bearer
  POST /v1/messages              send (bearer)
  GET  /v1/inbox                 list mine (bearer)
  GET  /v1/messages/{id}         read one (bearer)
  POST /v1/messages/{id}/ack     mark read (bearer)
  GET  /v1/stream                SSE push (bearer)

Repo: https://github.com/bfxavier/outbox