Core editor shortcuts become registry commands run by the single
useCommandShortcuts dispatcher: undo/redo, delete, duplicate (after +
select), copy/paste, Alt+arrow move, 1/2/3 device, Cmd+S/Shift+P/P site
commands and Cmd+/ cheat sheet. Tab/Esc no longer fire from buttons or
dialogs. Context menu labels come from formatShortcut.
Refs #39
