Also a detail-oriented person so I spot so I have the same superpower as your partner. I'm also the person who will notice when something isn't straight, or symmetrical, or things like that. I'll also notice if you have a new hair cut, new clothes, new shoes,... or if there is something new or unusual in general (using sight or sound, my other senses aren't that great :) providing it's a detail. Can't see the big picture most of the time.

I'm good at seeing how stuff can fit (or not!) or be best arranged in a room. Like evaluating available space and paths and stuff. Hm. I'd say also putting together outfits or matching colors.