fix: Polyline3D spline vertex flags and AttributeEntity/Definition DXF rotation

Polyline3D tessellation now separates spline-fit curve vertices (flag 8)
from frame control points (flag 16): the curve vertices form the rendered
wire while control points are exposed as key_vertices for snap. Polylines
without spline flags are unchanged.

DXF post-load fixup now also converts AttributeEntity and AttributeDefinition
rotation from degrees to radians (group code 50 bug), matching the existing
LinearDimension fix. Attribute text rendered from DXF files now has correct
orientation.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/io/mod.rs

@@ -170,13 +170,22 @@ pub fn save_dxf(doc: &CadDocument, path: &Path) -> Result<(), String> {
 
 // ── DXF post-load fixups ──────────────────────────────────────────────────
 
-/// The acadrust DXF reader stores LinearDimension.rotation directly from DXF
-/// group code 50, which is in degrees.  DWG and our own dimension-creation code
-/// store it in radians.  Convert so tessellation can call cos/sin uniformly.
+/// The acadrust DXF reader stores several rotation fields directly from DXF
+/// group code 50 in degrees, while DWG and our own creation code store radians.
+/// Apply to_radians() on load so tessellation can call cos/sin uniformly.
 fn fix_dxf_dimension_rotations(doc: &mut CadDocument) {
     for entity in doc.entities_mut() {
-        if let EntityType::Dimension(Dimension::Linear(d)) = entity {
-            d.rotation = d.rotation.to_radians();
+        match entity {
+            EntityType::Dimension(Dimension::Linear(d)) => {
+                d.rotation = d.rotation.to_radians();
+            }
+            EntityType::AttributeDefinition(a) => {
+                a.rotation = a.rotation.to_radians();
+            }
+            EntityType::AttributeEntity(a) => {
+                a.rotation = a.rotation.to_radians();
+            }
+            _ => {}
         }
     }
 }