v0.7.0

Added

• The panel is keyboard driven. Tab and up/down walk the display cards in
  the order shown, wrapping at the ends; left/right move the cursored
  display by 5%; Enter flashes it; Escape closes. Hovering a card aims
  the keys at it, so the arrows act on whatever is under the pointer.

Changed

• The neutral mark on each track is half as tall, sized off the slider knob so
  it stays visible at exactly 0%, where the knob parks on top of it.