Current cooldown record, in a game where I didn’t even find a Scriptorium, only the quill that produces scrolls after battle:
Update: can now confirm that 1s is the minimum cooldown on items. Pretty fun to use items with a 1s cooldown. I combined a 1s Pain Doll with a 1s cooldown version of the item to charge another item, which means that 1s after the battle the Pain Doll activated twice.