refactor(properties): Color above Layer; drop the Invisible toggle

Reorder the General group so Color precedes Layer. Remove the "Invisible"
row: the entity visibility flag (DXF code 60) is driven by dynamic-block
visibility states, not a manual per-object toggle — setting it from the
panel hid the object with no easy way to reselect it. The flag itself is
unchanged (dynamic blocks still set it, render/save still honour it, and
it stays settable programmatically).

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

src/scene/cache/properties.rs

@@ -31,16 +31,16 @@ pub fn general_section(entity: &EntityType) -> PropSection {
                 field: "handle",
                 value: PropValue::ReadOnly(common.handle.value().to_string()),
             },
-            Property {
-                label: "Layer".into(),
-                field: "layer",
-                value: PropValue::LayerChoice(common.layer.clone()),
-            },
             Property {
                 label: "Color".into(),
                 field: "color",
                 value: PropValue::ColorChoice(common.color),
             },
+            Property {
+                label: "Layer".into(),
+                field: "layer",
+                value: PropValue::LayerChoice(common.layer.clone()),
+            },
             Property {
                 label: "Linetype".into(),
                 field: "linetype",
@@ -90,15 +90,6 @@ pub fn general_section(entity: &EntityType) -> PropSection {
             .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
 }