Classification : Implement Batch API for model evaluation

Current Behavior
For evaluation of fine-tuned models, we currently use the Responses API synchronously to generate predictions. These predictions are then compared against the true labels of the corresponding questions. However, this synchronous setup is difficult to manage and would require building a complex system to make the whole process asynchronous and more reliable.

Proposed Improvement
Instead of relying on the synchronous approach, we can leverage the OpenAI Batch API. By sending all evaluation queries together as a batch, we can retrieve the predictions from the batch output file and then compare them against the true labels. This would simplify the workflow and make the evaluation process more scalable and efficient.

document to refer : https://docs.google.com/document/d/1y2WLRUm2dZaQMetvb31XpDH5HqteRe4UNpziG8pq608/edit?tab=t.lbfxo8c09bqd#bookmark=id.1ib6z5f31fld

リポジトリ内の現在の同期 Responses API 評価フローを確認し、その後、提案されているバッチワークフローについてリンク先の設計ドキュメントを参照してください。評価クエリが Batch API を通じて送信され、予測がバッチ出力ファイルから読み取られ、それらの予測が対応する正解ラベルと比較されれば完了です。