how to access workspace chat participant or codebase tool from my vscode extension?

[roshinimichael]

I have a vscode extension based on this chat sample: https://github.com/microsoft/vscode-extension-samples/tree/main/chat-sample
How can I access @workspace or #codebase to leverage code-context in extension prompt: https://code.visualstudio.com/docs/copilot/reference/workspace-context

Related feature request found: Chat: Allow a way for participants to direct requests to other participants · Issue #232837 · microsoft/vscode : "Right now, we're using OpenAI function calling to direct appropriate questions to a homemade workspace context plugin, that essentially just calls the copilot_codebase lmTool. It works, but it's not nearly as good an experience as what @workspace can do. For example, one thing we like that @workspace provides is linkification of the file references."