So Real List. Planning Urgent and Important in TickTick

Just as pedantry (for a kind of algebraic topology of lists?), there's a short exact sequence here:

  0 ↪ todolist ↪ checklist ↠ list ↠ 0
               f           g

`f` takes the active items of a todolist and decorates them as undone [ ] items, yielding a checklist

`g` takes a checklist and forgets entire undone [ ] items as well as the [x] of the done items, yielding a list

Exercise: does it split?