List AI Gateway routing rules

{
  "data": [
    {
      "attributes": {
        "created_at": "2026-08-24T12:00:00Z",
        "route_id": 123,
        "tiers": [
          {
            "ordering": "configured",
            "ordering_issue": "mixed",
            "targets": [
              {
                "id": 901,
                "model": "gpt-5.2-codex",
                "model_id": 101,
                "provider": "prod-us",
                "reasoning_level": "medium",
                "slug": "coding-fallback",
                "type": "model",
                "weight": 70
              }
            ]
          }
        ],
        "updated_at": "2026-08-24T12:00:00Z"
      },
      "id": "coding",
      "type": "routing-rules"
    }
  ]
}