Assistant: document customization options (chat modes, instructions, prompts) #9982
Description
We currently have a little bit of documentation on customizing the default prompt, but we'll want to expand this to capture what support we have for:
- custom chat modes
- MCP
- custom instructions
- any other ways to modify the system prompt
Related issues that may affect this documentation:
- Assistant: Provide an extensibility point for amending the system prompt #7725
- https://github.com/posit-dev/positron-builds/issues/367
- Assistant: Apply Copilot custom instructions files in all contexts #9563
In particular, we'll want to cover the affordances implemented in #9993.