Refactor widget components to call history transaction messages

Currently, the Svelte widget components just call "update" and "commit" which is a lossy simplification of the history system, and fails in the case of changing fonts and mapping old font styles to the supported styles of the new font because it produces an extra unavoidable history step.

Instead, we should call "update" plus each of the four(?) history events from the relevant components, particularly those where ongoing interaction can occur like number dragging and dropdown selection.