Create "interaction" toolbar and remove preview icon

The pencil icon for "edit mode" as well as the concept of "preview mode: has been causing a lot of confusion. There isn't really a meaningful or full preview mode in the way wobble web is implemented, as the overarching wobble layout is always present. In the future, if we want a more meaningful preview mode, I think it would make sense to open it in a second window.

Instead, it makes sense to define a set of different ways of interacting with the canvas. This opens the door for future tools, such as a global drawing tool as well as more experimental tools, such as the folk-js weak layout tool, or the magnet tool: https://wwwobble.org/live-2025/