feat: Convert to Sheet Metal takes a solid or a shelled body by its bend edges (#725)

Convert to Sheet Metal now takes a solid or a shelled body by its bend edges (`bends`): the faces reached from the fixed face across those edges become the sheet, keeping the part's envelope, with the flat pattern by the rule's K-factor and radius. Other edges between sheet faces are cut open. The result works with edge flanges, cuts, Unfold/Refold, the flat pattern and DXF. A conversion without `bends` is the plate conversion as before. The optional `bends` field is noted under format 17. Fixes #647.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/features.rs

@@ -394,6 +394,10 @@ fn add_feature_in(s: &mut Session, p: &Value, kind: FeatureKind, world: bool) ->
             (Vec::new(), solidcraft_doc::sheet::sheet_edge_names(&s.model.state(), &points))
         }
         FeatureKind::SheetHem { edges, .. } => (Vec::new(), solidcraft_doc::sheet::sheet_edge_names(&s.model.state(), edges)),
+        // A conversion's bend edges are edges of the body it converts.
+        FeatureKind::SheetConvert { body, bends, .. } if !bends.is_empty() => {
+            (Vec::new(), solidcraft_doc::sheet::bend_edge_names(&s.model.state(), body, bends))
+        }
         _ => (Vec::new(), Vec::new()),
     };
     let face_names = {