Copilot Chat web support

[joaomoreno]

We want to explore supporting a subset of Copilot Chat in VSCode for web.

[billti]

It would be great if it could support Agent mode and extension contributed tools (i.e., https://code.visualstudio.com/api/extension-guides/tools).

Our extension is entirely a web extension and all features (simulation, debugging, build, etc.) run great on desktop or in browser, and the extension also contributes a lot of tools such as fetching service status, submitting jobs, etc. (https://github.com/microsoft/qsharp/blob/main/vscode/package.json#L596). It would be awesome if this worked in the web copilot chat too.