v0.7.0

• Cleaner drag-state model (refines v0.6.0, closes #5): while a pointer
  holds the slider, both arrows take the engaged (hover) color — a plain
  tap on mobile no longer lights a single arrow. Actual movement (≥ 3px)
  narrows the highlight to the direction arrow; after 200 ms of
  standstill both arrows re-engage; release returns to neutral. Panel
  preview behaves identically.