Sketch on an origin plane faces the side you clicked (#1587)

Fixes #1586.

crates/engine/src/occurrences.rs

@@ -240,7 +240,7 @@ impl Session {
         let mut plane = plane;
         loop {
             match plane {
-                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => plane = base,
+                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => plane = base,
                 // A face attachment that names no exact source: which body it sits on is unknown,
                 // so none is taken from the view.
                 PlaneRef::Face { anchor: None, .. } => return none,