In a tilted 3D view a grip followed the cursor onto the screen plane
through the orbit target, so a circle or arc jumped to another radius and
a polyline vertex left its plane. A model-space grip now moves in the UCS
XY plane at its own elevation (the screen plane only when seen edge-on).
A solid stays drawn while its grip moves, and its own edges were still
snap candidates: a cone's base radius landed on its own side. The edited
entities are left out of the grip's snap set.
Fixes#1033
Co-Authored-By: Claude Opus 5.5 <[email protected]>