warmboot rail
  OUT  GET  /v1/boot?space=S[&since=][&budget=][&format=text]
       GET  /v1/delta?space=S&since=CURSOR
       GET  /v1/stream?space=S[&since=]        (SSE)
       GET  /v1/state?space=S
       GET  /v1/spaces
  IN   POST /v1/event?space=S                  (Bearer write token)