Frame quartet

Every other gallery in the library runs its photographs to the edge of their cell; here each one is inset inside a ruled plate with real white space around it, so the section reads as four framed prints on a wall rather than four tiles in a grid. The mat is made of two things and only two: a style.border on each plate group (currentColor, solid, 1px, written in both the block's settings and the rendered style= in the order the style engine emits them, border-color then border-style then border-width) and var:preset|spacing|40 of padding on all four sides.

It survives colourlessness because the frame is a currentColor hairline. currentColor cannot blank, needs no chain and follows whatever text colour the theme puts on the band, so the rule is always exactly as dark as the caption beside it: in a light theme it is a fine ink line on paper, in a dark one a fine pale line on ink, and in both it is the same idea. The white space inside it is the band's own ground, which is a base chain, so the mat is never painted and never needs to be.

It survives 390px because the mat is padding, not layout. Below 782px core stacks the two core/columns rows, each column becomes its own flex line, and the four plates become a vertical run of four. Each one keeps its padding and its rule at full strength, so a phone shows the same framed print at a different rhythm: one wide mat after another down the page, instead of two beside two. Nothing is dropped and nothing collapses; only the number of prints per line changes.