The quieting doctrine (gf-69c — what makes a chart look finished)
No per-mark totals — gridlines do the work; numbers live in the native
<title> tooltips, plus at most ONE selective direct label (the endpoint,
the max) where the question demands it.
A legend toggle keeps IDENTICAL content in both states — no layout
shift (the outline-not-border spirit); state rides data-ui-state.
Legend = tags tinted by their series hue on a borderless .surface at
--lift: -0.2, overlaid in RESERVED margin space (mr accounts for it).
Title = hgroup with h3 + small, HTML over the chart (.chart-host /
.chart-title / .chart-legend, engine recipes in static/system.css), never
drawn in the SVG.
A single series gets NO legend — the title names it.
Sorted marks wherever order is free (ranking reads instantly); ONE axis,
always — two measures of different scale are two charts.