Add the option to toggle preview/code mode for markdown in the assistant panel.

[RealCrayfish]

When using the assistant panel I've noticed that it can be hard to distinguish between different files/code blocks provided by assistants due to the panel displaying raw markdown rather than preview. With this I also suggest adding buttons to code blocks for copying code and collapsing blocks.

[ZemichaelMD]

I really hope to see this! It would be easier to see what the assistant generates and easier to interact, copy and apply. It would also make it easier for future development of agentic assistant.