Change third party github actions to target specific commits rather than tags

まだ誰も着手していません。

We should pin our third party github actions to a specific commit, rather than a tag as we currently do.

This is a cybersecurity measure [recommended by GitHub](https://docs.github.com/en/actions/reference/security/secure-use#using-third-party-actions):
> The individual jobs in a workflow can interact with (and compromise) other jobs. For example, a job querying the environment variables used by a later job, writing files to a shared directory that a later job processes, or even more directly by interacting with the Docker socket and inspecting other running containers and executing commands in them.

> This means that a compromise of a single action within a workflow can be very significant, as that compromised action would have access to all secrets configured on your repository, and may be able to use the GITHUB_TOKEN to write to the repository. Consequently, there is significant risk in sourcing actions from third-party repositories on GitHub. For information on some of the steps an attacker could take, see [Secure use reference](https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#potential-impact-of-a-compromised-runner).

In our workflows, we have some third party actions used like such:
```
- name: Install uv
uses: astral-sh/setup-uv@v7
```

まず、astral-sh/setup-uv@v7 の例を含め、リポジトリのワークフローファイルでサードパーティの GitHub Actions を検索します。各サードパーティ action をタグではなく特定の commit に pin し、その後、利用可能なワークフローチェックを実行して、引き続き成功することを確認します。

索引モデルが issue の本文から書いたものです。