This PR updates the Gemini provider to treat a `prompt_feedback.block_reason` as a refusal, as Gemini does not seem to return a `stop_reason` to use in this case. <img width="639" height="162" alt="Screenshot 2025-09-22 at 4 23 15 PM" src="https://github.com/user-attachments/assets/7a86d67e-06c1-49ea-b58f-fa80666f0f8c" /> Previously this would just result in no feedback to the user. Release Notes: - Added an error message when a Gemini response contains a `block_reason`.