Removed the medium-mode -12px details margin compensation — it
under/over-shot depending on grid row sizing. Replaced with a
:has() rule: when the user expands To/Cc, the From row gets
min-height 92px (matching the cluster's 2-row max height). Row 1
becomes the same size whether the cluster is 1 row (wide) or 2
rows (narrow), so resizing across the 600px wrap breakpoint no
longer makes To/Cc shoot up 4px.
6edcc07c1b