Get Eval Type Instructions By Slug

Retrieve instructions for a specific eval type by its slug.

Args: eval_type_slug (str): Slug identifier for the eval type.

Returns: list[AiInstruction]: List of AI instructions for the eval type.

Raises: AymaraAPIError: If the eval type is not found.

Example: GET /api/eval-types/-/instructions?eval_type_slug=...