v0.10.0 - real coordinator + exactly-once delivery

Real General coordinator (full haiku agent, fresh session each request, fleet_command + Bash/Write to create folders/scaffold/manage fleet). Command routing so commands never hit the coordinator. /agent/{name}/inject for external alert push (tac). Exactly-once delivery: per-agent cursor + replay on reconnect + consumer id-dedup (persisted high-water) + ack; receiver retries on backend-down. No loss, no duplicates.