The Windows shape clamp used the nominal PET_WINDOW_HEIGHT constant. Renderer
regions are measured against the live viewport, so once the content area was
taller than that constant the mascot -- which sits flush with the viewport
bottom -- got sliced off from below, while the task badge kept its own
unclamped rect and stayed visible. Clamp the shape to the real content box.
Dragging also moved the window with setPosition, which Windows resolves as
getSize() + setBounds(); that DIP round trip grows the window a pixel at a
time on fractional display scaling, and the drag timer fires every 16ms.
Restate the recorded size on every tick so dragging stays size-neutral.
