feat(properties): show Thickness in the General group

Thickness (DXF 39) is a General-group property in the palette, but it is
stored per-entity, so it was previously shown (inconsistently) only in the
Geometry section of a few entities. Surface it in General for every entity
type that carries an extrusion thickness (arc, circle, line, lwpolyline,
point, polyface mesh, 2D polyline, shape, 2D solid, text) via
entity_thickness / set_entity_thickness, routed through apply_common_prop.

Removes the now-duplicate Thickness rows (and dead apply arms) from the
arc/circle/shape/solid Geometry sections so it is never shown twice.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/entities/arc.rs

@@ -170,7 +170,6 @@ fn properties(arc: &Arc) -> Vec<PropSection> {
             edit("Normal X", "normal_x", arc.normal.x),
             edit("Normal Y", "normal_y", arc.normal.y),
             edit("Normal Z", "normal_z", arc.normal.z),
-            edit("Thickness", "thickness", arc.thickness),
         ],
     }]
 }
@@ -189,7 +188,6 @@ fn apply_geom_prop(arc: &mut Arc, field: &str, value: &str) {
         "normal_x" => arc.normal.x = v,
         "normal_y" => arc.normal.y = v,
         "normal_z" => arc.normal.z = v,
-        "thickness" => arc.thickness = v,
         _ => {}
     }
 }

src/entities/circle.rs

@@ -138,7 +138,6 @@ fn properties(circle: &Circle) -> Vec<PropSection> {
             edit("Normal X", "normal_x", circle.normal.x),
             edit("Normal Y", "normal_y", circle.normal.y),
             edit("Normal Z", "normal_z", circle.normal.z),
-            edit("Thickness", "thickness", circle.thickness),
         ],
     }]
 }
@@ -155,7 +154,6 @@ fn apply_geom_prop(circle: &mut Circle, field: &str, value: &str) {
         "normal_x" => circle.normal.x = v,
         "normal_y" => circle.normal.y = v,
         "normal_z" => circle.normal.z = v,
-        "thickness" => circle.thickness = v,
         _ => {}
     }
 }

src/entities/shape.rs

@@ -144,7 +144,6 @@ impl PropertyEditable for Shape {
                 edit("Rotation", "shp_rot", self.rotation.to_degrees()),
                 edit("Width Factor", "shp_xs", self.relative_x_scale),
                 edit("Oblique Angle", "shp_ob", self.oblique_angle.to_degrees()),
-                edit("Thickness", "shp_th", self.thickness),
                 edit("Normal X", "shp_nx", self.normal.x),
                 edit("Normal Y", "shp_ny", self.normal.y),
                 edit("Normal Z", "shp_nz", self.normal.z),
@@ -168,7 +167,6 @@ impl PropertyEditable for Shape {
             "shp_rot" => self.rotation = v.to_radians(),
             "shp_xs" if v.abs() > 1e-9 => self.relative_x_scale = v,
             "shp_ob" => self.oblique_angle = v.to_radians(),
-            "shp_th" => self.thickness = v,
             "shp_nx" => self.normal.x = v,
             "shp_ny" => self.normal.y = v,
             "shp_nz" => self.normal.z = v,

src/entities/solid.rs

@@ -117,7 +117,6 @@ impl PropertyEditable for Solid {
                 edit("Point 4 Y", "sl_p4y", self.fourth_corner.y),
                 edit("Point 4 Z", "sl_p4z", self.fourth_corner.z),
                 ro("Elevation", "sl_elev", format!("{:.4}", elevation)),
-                edit("Thickness", "sl_thick", self.thickness),
             ],
         }]
     }
@@ -139,7 +138,6 @@ impl PropertyEditable for Solid {
             "sl_p4x" => self.fourth_corner.x = v,
             "sl_p4y" => self.fourth_corner.y = v,
             "sl_p4z" => self.fourth_corner.z = v,
-            "sl_thick" => self.thickness = v,
             _ => {}
         }
     }

src/scene/cache/properties.rs

@@ -23,7 +23,7 @@ pub fn general_section(entity: &EntityType) -> PropSection {
         })
         .unwrap_or_default();
 
-    PropSection {
+    let mut section = PropSection {
         title: "General".into(),
         props: vec![
             Property {
@@ -78,16 +78,28 @@ pub fn general_section(entity: &EntityType) -> PropSection {
                 field: "hyperlink",
                 value: PropValue::ReadOnly(hyperlink),
             },
-            Property {
-                label: "Invisible".into(),
-                field: "invisible",
-                value: PropValue::BoolToggle {
-                    field: "invisible",
-                    value: common.invisible,
-                },
-            },
         ],
+    };
+
+    // Thickness (DXF 39) is a General-group property, but only the entity
+    // types that carry an extrusion thickness expose it (line, circle, arc,
+    // polyline, text, 2D solid, …). Show it right after Hyperlink for those.
+    if let Some(t) = crate::scene::view::dispatch::entity_thickness(entity) {
+        section
+            .props
+            .push(crate::entities::common::edit_prop("Thickness", "thickness", t));
     }
+
+    section.props.push(Property {
+        label: "Invisible".into(),
+        field: "invisible",
+        value: PropValue::BoolToggle {
+            field: "invisible",
+            value: common.invisible,
+        },
+    });
+
+    section
 }
 
 /// The "3D Visualization" group (Material + Shadow display), common to every

src/scene/view/dispatch.rs

@@ -56,6 +56,49 @@ pub fn apply_common_prop(entity: &mut EntityType, field: &str, value: &str) {
                     .set_transparency(Transparency::new(alpha));
             }
         }
+        "thickness" => {
+            if let Ok(v) = value.trim().parse::<f64>() {
+                set_entity_thickness(entity, v);
+            }
+        }
+        _ => {}
+    }
+}
+
+/// The extrusion thickness (DXF 39) of the entities that carry one, or `None`
+/// for entity types that have none. Thickness is a per-entity field but is
+/// surfaced in the General group (as in a standard properties palette), so
+/// this bridges the two.
+pub fn entity_thickness(entity: &EntityType) -> Option<f64> {
+    Some(match entity {
+        EntityType::Arc(e) => e.thickness,
+        EntityType::Circle(e) => e.thickness,
+        EntityType::Line(e) => e.thickness,
+        EntityType::LwPolyline(e) => e.thickness,
+        EntityType::Point(e) => e.thickness,
+        EntityType::PolyfaceMesh(e) => e.thickness,
+        EntityType::Polyline2D(e) => e.thickness,
+        EntityType::Shape(e) => e.thickness,
+        EntityType::Solid(e) => e.thickness,
+        EntityType::Text(e) => e.thickness,
+        _ => return None,
+    })
+}
+
+/// Set the extrusion thickness on the entity types that carry one; no-op for
+/// the rest.
+pub fn set_entity_thickness(entity: &mut EntityType, v: f64) {
+    match entity {
+        EntityType::Arc(e) => e.thickness = v,
+        EntityType::Circle(e) => e.thickness = v,
+        EntityType::Line(e) => e.thickness = v,
+        EntityType::LwPolyline(e) => e.thickness = v,
+        EntityType::Point(e) => e.thickness = v,
+        EntityType::PolyfaceMesh(e) => e.thickness = v,
+        EntityType::Polyline2D(e) => e.thickness = v,
+        EntityType::Shape(e) => e.thickness = v,
+        EntityType::Solid(e) => e.thickness = v,
+        EntityType::Text(e) => e.thickness = v,
         _ => {}
     }
 }