Visual static representation of a horizontal slider. Track splits
into left fill (accent) + 20×20 thumb (white + accent stroke) +
right remaining (slate), all aligned on a 20px track wrap. Optional
label + value readout row above; `value_suffix` renders "60%" /
"128px" / "0°" style readouts. Pixel math: fill = (width-20) * pct,
auto-collapses fill or remaining at either extreme.
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