So I have identified the following possible solutions:
1. The door dealers told me they could cut the door down at a cost of $67, though it sounded like taking an inch off was getting to a limit where the standard storm door wouldn't fit.
2. I read in this group that somebody cuts the header back to make room for therma-tru doors which tend to be taller than everybody else. Is that a reasonable thing to do? (Wall is not structural.)
3. I could reframe the rough opening which seems like a bit of work.
4. I could lower the subfloor. As it happens, the subfloor is rotted out and needs to be replaced anyway, so I could replace it by something thinner right where the door is to sink the door into the floor. (Floor is vinyl tile on top of 1/4" plywood on top of 3/4" subfloor.) I could support this with blocking underneath.
Anything on this list reasonable?