[WIP] Add gpt-oss-safeguard support

[turt2live]

Requires #58 (this PR's base) (landed)

This is a work in progress and may change.

Setup guide: https://cookbook.openai.com/articles/gpt-oss-safeguard-guide (I used LM Studio)

Pull Request Checklist

• Pull request is based on the main branch.
• Pull request title describes the changes in a way a user would understand. For example, "Fix keywords filter not applying" instead of "Read keywords slice in a loop".
• Code style matches surrounding code.
• Tests are added for new code (and existing code) if possible.
  • If not possible, please explain why in your PR description.
• The CI checks pass.