ResponseTextAnnotationDeltaEvent

{
    "type": "response.output_text.annotation.added",
    "item_id": "string",
    "output_index": 0,
    "content_index": 0,
    "annotation_index": 0,
    "annotation": {
        "type": "file_citation",
        "file_id": "string",
        "index": 0
    }
}