Constant SKETCH_ORIGIN_POINT_ID 

pub const SKETCH_ORIGIN_POINT_ID: &str = "origin";

The reserved id of every sketch’s PART ORIGIN reference point: world (0, 0, 0) projected onto the sketch plane. The editor adds it on entry as a fixed, grounded, construction external reference, so geometry can be constrained to the origin. The sketch feature re-projects it onto the resolved frame before solving and never publishes it — it exists only inside the sketch (no scene point, no hole center, no 3D display).