On macOS the screenshot path lacked a counterpart to win32's
ClientToScreen. Detecting a target inside a cropped GrabScreen(bbox)
image and feeding the in-image (px,py) straight to Click silently
mis-clicks because the crop-origin offset is dropped.
- add CropToScreen(bbox, x, y): in-crop coords -> absolute physical
coords (pure crop-origin add, no scaling)
- GrabScreen docstring: warn about the crop-origin trap and not to
hand-roll screencapture -R (it takes logical points)
- Click 0%-pixel-change warning now names the common causes
- ljqCtrl_sop.md: add macOS subsection mirroring the win32 trap note