COPYCLIP/CUTCLIP used the mean of each entity's bounding-box centre as the
paste anchor. Standard clipboard behaviour puts the lower-left corner of the
box enclosing all copied items under the cursor. Union each entity's bbox min
corner instead, and rename clipboard_centroid -> clipboard_base (COPYBASE also
stores a picked point there, so "centroid" was inaccurate).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
c249a99d4c