Between paths, the Pen now adds an anchor where a click lands on a
segment of a selected path and deletes the anchor a click lands on,
with the add and delete cursors while hovering, as in the reference
app. The ends of a selected open path still continue it. Shift held,
or General > Disable Auto Add/Delete (a stored preference nothing read
until now, passed to tools as ToolContext::auto_add_delete), starts a
new path instead.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>