The zone is one paragraph, so its mark sizes every line of the band. Runs that agree on a font now set that strut (applyUniformRunFont, as the body already does), the zone schema carries blockFontSize so it renders, and hfReachPx measures a line by the family's natural height instead of a flat 1.15. A 10pt footer reserved 12pt lines and sat 1.6mm high on every page.