Measure zero-point offsets between exposures

This could be due to flexure or other sources of variance between observations.

This could produce a list and correct the WCS accordingly.

The issue names no file, test, or entry point. Start by locating the exposure and WCS reduction workflow, then determine how zero-point offsets should be measured between exposures. Done means producing an offset list and correcting the WCS accordingly.

Written by the indexing model from the issue text.