Response envelope & errors

{
  ok: true
  data: unknown              // the operation's result
  asOf: string               // ISO timestamp
  asOfBasis: string          // "server-time" for normal operations
  caveat?: Caveat[]          // see below
  trust?: {
    rpc?: {
      route: "quicknode" | "quicknode-mock" | "fallback"
      methods_quicknode: number
      methods_fallback: number
    }
    screen?: {
      provider: "aws-bedrock-guardrails" | "mock" | "off" | "unavailable"
      fields_checked: number
      fields_blocked: number
      max_score?: number
    }
  }
}

{
  ok: false
  error: {
    service: string          // e.g. "xrpl", "auth", "policy", "docs"
    kind: "error" | "soft-empty"
    message: string
    code?: string
    hint?: string
  }
}