Fix potential inaccuracy bug

I don't think this is an actual bug, since the conversion from local to
global point should be deterministic. Still, at the very least, this is
restoring the code to its original intention.

experiments/2025-03-18/src/geometry/sketch.rs

@@ -42,7 +42,7 @@ impl Sketch {
                 let vertex = Handle::new(Vertex::new(point_global));
 
                 vertices_by_local_point
-                    .entry(point_global)
+                    .entry(point_local)
                     .or_default()
                     .push(vertex.clone());