[AI Tutor] CT-503: Format OpenAI responses using markdown

[ebeastlake]

The following PR formats the AI response in markdown, so code blocks are properly rendered.

Links

Jira ticket: https://codedotorg.atlassian.net/browse/CT-503

Testing story

Follow-up work

We want to add the ability to copy a code block -- this is in a separate PR because it's riskier and requires refactoring the SafeMarkdown component.

PR Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[ebeastlake]

The code block and horizontal rule don't seem exactly right in the list, but code blocks are rendering appropriately in normal responses and the horizontal rule is unlikely to get used, I think. Is it worth spending time to investigate?

[molly-moen]

Looks good to me! For the incorrect markdown in the list, is the text being sent correct markdown or is the ai messing up? My guess is it's the AI's fault...

[ebeastlake]

I confirmed it's the AI's fault! It was escaping the backticks on the code blocks (i.e., ```) and adding triple backticks around the horizontal rule. Without those, they each render correctly.