Improve Handbook Assistant

[vzakaznikov]

Improve Handbook Assistant:

• Add support for streaming responses (in progress)
• Investigate support for reference links used to generate the answer (in progress)
• Add support for follow up questions (context history)
• Add support for Markdown renderer
• Fix scrolling issue when the answer is being generated
• Investigate usage of the cheaper gpt-4o-mini model. Moved to using gpt-4o.

[vzakaznikov]

@Selfeer, can you take a look at getting streaming to work?