The stripe began one row late: regionsAt counted the second body row as the
first band. Probed on a five-row fixture with a red band1Horz — LibreOffice
shades row 0 where the style paints no header region, and the row under the
header where it does.
The corpus cannot see this (no fixture uses the editor's own registry), so it
stayed at 739; checked by eye and by the unit test's inverted expectations. A
document with a table style assigned re-bands on its next open.