Initial implementation of an artifact system which allows users
to generate HTML pages directly from the AI persona.

FEATURE: support tool progress callbacks

This is anthropic only for now, but we can get a callback as tool
is completing, this gives us the ability to show progress to user
as the function is populating.

work in progress

Revert "work in progress"

This reverts commit 30ebe56.

Revert "FEATURE: support tool progress callbacks"

This reverts commit fd7ccfd.

- post streamer ensures we don't have half completed stuff on screen when a tool is slow
- reimplemnt xml tools to have a more relaxed parse