Refactor-Legacy-Callbacks-Async

The model receives the prompt (and optional system message). The run uses scorer rubric_json_metrics with the JSON configuration below. Pass/fail and partial credit are determined entirely by that scorer against the model output; no human grading.

Return JSON only with keys refactor, rationale, tests. Refactor nested Node-style callbacks into async/await while preserving error-first behavior and cleanup ordering.

{
  "metrics": {
    "visible": {
      "checks": [
        {
          "contains": [
            "async/await"
          ]
        },
        {
          "contains": [
            "callbacks"
          ]
        },
        {
          "contains": [
            "error-first"
          ]
        }
      ]
    },
    "hidden": {
      "checks": [
        {
          "contains": [
            "cleanup ordering"
          ]
        },
        {
          "contains": [
            "nested"
          ]
        },
        {
          "contains": [
            "preserve"
          ]
        }
      ]
    },
    "intent": {
      "checks": [
        {
          "contains": [
            "modernization"
          ]
        },
        {
          "contains": [
            "control flow"
          ]
        },
        {
          "contains": [
            "legacy"
          ]
        }
      ]
    }
  }
}