Right-click a running task icon to pin the app to the dock
favourites bar. Pinned apps show a "Remove from Dock" action.
The dock overlay renders as a LayerTop window so context menus
and the dock itself stay above application windows. Menus use
popupType Window to avoid clipping inside the narrow dock
surface.
Add thumbnail preview feature and the three convergence bug
fixes: minimized windows staying in dock, drawer overlay not
covering dock icons, and new-process launch behaviour.
