allow mcp servers to send viewable updates to the frontend #76
Description
as part of a status update, the mcp could trigger the canvas to show something (like a plot in html or an image)
this allows longer running mcp servers to better show progress than just updating a single "system" message.
Also, support sending richer system messages where it displaces as anew item on the chat history.
Follow a similar setup for the final return type from a mcp function where there are fields that indicate how the frontend should respond. (ie. files, canvas display).