Nucleus rect of each cell, in cell-index order (matches cells).
The whole color bar (the bands stack to fill it).
The two color-bar gutter marker discs (left, right), as bounding rects.
The visible ellipse overlay's axis-aligned bounding box: the bbox of the ROTATED ellipse, clipped to the grid (the ellipse is drawn under the grid clip-path). Always present — the ellipse is always drawn.
The grid background rect (the "background color" feature).
The root SVG viewBox, "0 0 W H".
Pixel geometry of each highlightable feature, in viewBox user-units — so a comparison/walk UI can draw a focus ring AROUND any feature without parsing the rendered SVG (it never mutates the closed-profile artifact). Derived in the same model pass as the structural channels, and cross-checked against a freshly rendered SVG by
test/integration/describe-consistency.