Undo and redo in the site editor

The Site editor now has "Undo" and "Redo" (and Cmd/Ctrl+Z): step back through your draft changes one at a time while the page is open. If someone else changed the same thing in the meantime, the editor says so instead of overwriting their change. The same goes for the editor open in two tabs: the older one can no longer quietly remove a newer change, and asks which version to keep.

Also in the editor: the preview always shows your store's font, a new section comes into view straight away, banner names and text positions are clearer, and a setting set back to the live value leaves the draft.