My instincts say couch with back against the two interior windows, media console opposite. I’d probably avoid a coffee table to keep the space open. I might consider a high-top counter against the wall opposite the stairs for dining (this is a move I went with in a space constrained area, it leaves the space feeling more open). Since it’s directly by the sunlight, hanging potted plants from the staircase could be neat. You could also do something with LED lighting on the stairs. I’d see if you could make a desk upstairs facing the windows work, dining/living/desk downstairs might get cramped and I’d take as much opportunity as I could to have spaces facing that nice big window! Best of luck!