feat(entities): surface remaining 3D fields + add Mesh render path

Closes out the 3D-entity audit. Mesh (modern SubD mesh) gained a full
render impl since it had no TruckConvertible / Grippable / PropertyEditable
hookup at all — it was silently dropped on open. Remaining mesh-style
entities pick up the few fields the parser populated:

- Mesh (SubD): wireframe + face-fan fill_tris rendering, per-vertex grips,
  Properties panel surfaces version, subdivision_level, blend_crease,
  creased-edge count, vertex / face / edge counts; wired into the
  Transformable / Grippable / PropertyEditable / TruckConvertible
  dispatch in entities/traits.rs
- Polyline3D: smooth_type, default_start_width, default_end_width,
  mesh_m_count, mesh_n_count, smooth_m_density, smooth_n_density
  (widths editable)
- PolygonMesh: smooth_type, m/n_smooth_density, elevation, normal
- PolyfaceMesh: smooth_surface, seqend_handle, elevation, normal,
  thickness

Solid3D / Region / Body's uid + silhouettes + history_handle were
included in the prior 2D commit since they share the same file.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/entities/polyline.rs

@@ -520,10 +520,32 @@ impl Grippable for Polyline3D {
 
 impl PropertyEditable for Polyline3D {
     fn geometry_properties(&self, _text_style_names: &[String]) -> PropSection {
+        use acadrust::entities::polyline3d::SmoothSurfaceType as SST;
+        let smooth = match self.smooth_type {
+            SST::None => "None",
+            SST::QuadraticBSpline => "Quadratic",
+            SST::CubicBSpline => "Cubic",
+            SST::Bezier => "Bezier",
+        };
         PropSection {
             title: "Geometry".into(),
             props: vec![
                 ro("Vertices", "vertices", self.vertices.len().to_string()),
+                edit("Default Start W", "pl3_start_w", self.default_start_width),
+                edit("Default End W", "pl3_end_w", self.default_end_width),
+                ro("Smooth", "pl3_smooth", smooth),
+                ro("Mesh M", "pl3_mesh_m", self.mesh_m_count.to_string()),
+                ro("Mesh N", "pl3_mesh_n", self.mesh_n_count.to_string()),
+                ro(
+                    "Smooth M Density",
+                    "pl3_smooth_m",
+                    self.smooth_m_density.to_string(),
+                ),
+                ro(
+                    "Smooth N Density",
+                    "pl3_smooth_n",
+                    self.smooth_n_density.to_string(),
+                ),
                 Property {
                     label: "Closed".into(),
                     field: "pl3_closed",
@@ -548,6 +570,14 @@ impl PropertyEditable for Polyline3D {
             } else {
                 self.open();
             }
+            return;
+        }
+        if let Ok(v) = value.trim().parse::<f64>() {
+            match field {
+                "pl3_start_w" if v >= 0.0 => self.default_start_width = v,
+                "pl3_end_w" if v >= 0.0 => self.default_end_width = v,
+                _ => {}
+            }
         }
     }
 }