v0.27.0

Fixed

• Desktop widget: Sleep / Wake, the tracking mode and speed chips and zoom react at once instead of
  after the next state event (1-3 s with obsbot4linux 0.13.2). It now uses the same optimistic
  values as the popout, held until an event confirms them or 3 s have passed; the mechanism is
  shared (OptimisticState.qml) (#91).
• Preview hint while the camera sleeps: the button is "Start preview" instead of "Wake camera".
  Opening the stream wakes the camera, so one click is enough; the hint shows "Waking camera…"
  until the first frame (at most 8 s), and the controls switch on at once (#93).