Error Codes - Lithtrix

All errors use a consistent envelope:

{
  "status": "error",
  "error_code": "MACHINE_READABLE_CODE",
  "message": "Human-readable description."
}

Code	HTTP	Description
`INVALID_API_KEY`	401	Key missing or not recognised
`RATE_LIMIT_EXCEEDED`	429	Per-minute limit hit
`OVER_LIMIT`	—	Lifetime cap reached (returned in usage object, not as error HTTP status)
`AGENT_ALREADY_EXISTS`	409	Name + owner pair already registered
`UPSTREAM_ERROR`	502	Brave Search error
`SERVICE_UNAVAILABLE`	503	Circuit breaker open