Templates live in the app package, so the chart types and renderer must
be exported. Also anchors the y-axis at zero, left-pads shorter series so
multi-series charts stay aligned, escapes text nodes, renders a
'collecting data' placeholder before enough samples exist, and adds a
seconds unit for latency quantiles.
Extends the existing sparklineSVG approach into a full chart helper
with axes, gridlines, multi-series lines/areas, legends, threshold
lines, and unit formatters (bytes, bps, ms, pct). No JS chart library;
safe to inline in templ pages.
Chris Lu