A 3D effect on a fill or stroke worked on copies of the object's fills
and strokes, and the copies were looked up among the object's items by
identity, so a live-effect plug-in before that 3D effect was given
`_context.item` "object" and a deferred stage there was listed with no
item. The drawn art, the 3D meshes and Expand as Wireframes now pass the
original item, so the plug-in is given `{"fill": i}` or `{"stroke": i}`
as docs/plugins.md describes. The paints of a type's first run still have
no item.