HFI processing: calculate high hfi areas runs a long time

**Describe the task**
I noticed that processing HFI tiffs with the calculate high HFI areas runs a long time (waited 15+ minutes before cancelling).

**Acceptance Criteria**
- [ ] Figure out what's causing it to run so long
- [ ] Make it not run so long

**Additional context**
- Add any other context about the task here.
- Or here

Begin at the “calculate high HFI areas” entry point and reproduce the 15+ minute behavior with an HFI TIFF. Profile that processing to identify the cause; done means the calculation no longer runs so long, as required by the issue’s acceptance criteria.

Written by the indexing model from the issue text.