feat: stabilize face attachments and closed spline workflows

crates/engine/src/cmd/component_clone.rs

@@ -346,6 +346,16 @@ pub(super) fn paste(
         {
             face.author_path = cloned_path(&source, &face.author_path, component, &clone_path, &occurrences)?;
         }
+        if let (FeatureKind::Sketch { plane, .. }, FeatureKind::Sketch { plane: old_plane, .. }) = (&mut f.kind, &old.kind)
+            && let (Some(anchor), Some(original)) = (super::sketch::face::anchor_mut(plane), super::sketch::face::anchor(old_plane))
+        {
+            if bodies.contains_key(&original.target.body) {
+                anchor.component =
+                    *components.get(&original.component).ok_or_else(|| bad(CMD, "anchored source component is outside copied graph"))?;
+                anchor.path = cloned_path(&source, &original.path, component, &clone_path, &occurrences)?;
+            }
+            anchor.author_path = cloned_path(&source, &original.author_path, component, &clone_path, &occurrences)?;
+        }
         if let Some(slot) = scratch.doc_mut().feature_mut(f.id) {
             *slot = f;
         }
@@ -473,6 +483,15 @@ pub(super) fn paste(
                 }
             }
         }
+        if let FeatureKind::Sketch { plane, .. } = &feature.kind
+            && let Some(anchor) = super::sketch::face::anchor(plane)
+            && !bodies.contains_key(&anchor.target.body)
+        {
+            notices.push(format!(
+                "{} retains external exact face attachment to {} (producer {})",
+                feature.name, anchor.target.body, anchor.target.origin_feature
+            ));
+        }
         for id in feature.kind.input_sketches() {
             if !features.contains_key(&id) {
                 notices.push(format!("{} retains an external sketch reference to {id}", feature.name));