SmartCollapse 1.3.0

feat(peek): give Windows' peek back when per-monitor peek stops

Windows' own "Peek at desktop" used to be switched off once on first
start, and the user had to turn it back on by hand. Now SmartCollapse
only borrows it while its own per-monitor peek is running:

- Switch Windows' peek off when hover peek is active, and back on when
  SmartCollapse is paused, hover peek is unticked, or the app exits.
- Restore it only if SmartCollapse switched it off (tracked with the
  WindowsPeekBorrowed setting). This replaces the one-time PeekHandled
  logic.
- If the user ticked Windows' peek again in the meantime, leave it on
  and turn hover peek off.
- On WM_ENDSESSION, restore the setting without broadcasting, because
  the process ends without leaving the message loop.
- On normal exit, restore it before the mutex is released, so an
  instance started with --replace borrows it only after that.
- Replace taskbar::TurnOffPeek with SetNativePeek(on, notify), which
  can switch the setting either way and optionally skip the
  WM_SETTINGCHANGE broadcast.
- Update the README to describe the new behavior.