Error Envelopes

JSON commands return structured failures:

{
  "ok": false,
  "errors": [
    {
      "code": "TASK_NOT_FOUND",
      "message": "Task DOC-PROJECT-001 was not found.",
      "taskId": "DOC-PROJECT-001"
    }
  ]
}

Fields may include:

code
message
taskId
path
stepId

Agents should branch on code and show message to humans.