Path tools should filter out snapping to the procedurally generated contents of its own layer

For example, a *Sample Points* node which generates circles on the inside of a shape. If you use the Path tool to modify that shape, it wants to snap to is own circles. We only want the Path tool snapping dragged points to other points in the same vector path, not the generated shapes that are derived from it.

Start by tracing the Path tool's snapping behavior and how it distinguishes points in the edited vector path from procedurally generated shapes in the same layer. Done means dragged points snap to other points in the same vector path but not to shapes generated from it; verify the behavior with the Sample Points example described in the issue.

Written by the indexing model from the issue text.