v4.28.1 — Smooth multi-series price updates

Fixed

• Restore smooth LiveChartSeries price updates after the 4.28.0 regression:
  ordinary live updates now ease the dot and newest drawn sample together,
  including feeds that append a matching recorded point. Source history stays
  unchanged and the line no longer bends back from a snapped point to a lagging
  dot. Explicit replay heads, static rendering, smoothing={1} and snapKey
  retain their existing behavior.