Merge tool-paths (or polylines) into ONE :class:compas.geometry.Polyline, in order.
Every tool-path begins and ends at its safe-Z height, so joining them
end-to-start gives a clean rapid at safe Z between cuts -- no diagonal dive
through the stock. Accepts tool-path objects (anything with a .path) or
raw polylines. Consecutive coincident points are dropped. With home (the
default) the merged path traverses back at safe Z to the global start, so the
whole job ENDS where it began.