feat(entities): surface remaining 2D + Region fields in properties

Closes out the 2D-entity audit (and the Region partner that ships next
to Solid3D / Body). Round-trip-only metadata fields plus a few editable
ones gain Properties-panel rows so the values the parser populates are
visible and don't get silently dropped on save:

- Hatch: seed_points count, pixel_size, normal
- Polyline2D: smooth_surface, default_start_width, default_end_width,
  thickness, normal (with editors for the widths/thickness)
- Region: uid, silhouettes (shared file with Solid3D / Body)
- Underlay: clip_inverted
- RasterImage: class_version, definition_handle, definition_reactor_handle
- Wipeout: class_version, clip_mode, definition_handle,
  definition_reactor_handle
- Leader: annotation_handle, override_color
- Tolerance: dimension_style_name, dimension_style_handle, dimension_gap,
  text_height (editable), direction, normal
- MLine: style_handle, style_element_count, justification picker
- Ole2Frame: version, source_application, binary_data size, dwg_mode,
  dwg_trailing_byte, is_paper_space
- Viewport: snap_base/spacing/angle, twist_angle, front/back clip Z,
  circle_sides, grid_flags, grid_major, base_ucs_handle, ucs_ortho_type,
  background_handle, shade_plot_handle, visual_style_handle,
  default_lighting, default_lighting_type, ambient_color (with editors
  for the snap / clip / circle_sides values)

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

src/entities/mline.rs

@@ -156,12 +156,41 @@ impl Grippable for MLine {
 
 impl PropertyEditable for MLine {
     fn geometry_properties(&self, _text_style_names: &[String]) -> PropSection {
+        let just_str = match self.justification {
+            acadrust::entities::MLineJustification::Top => "Top",
+            acadrust::entities::MLineJustification::Zero => "Zero",
+            acadrust::entities::MLineJustification::Bottom => "Bottom",
+        };
         PropSection {
             title: "Geometry".into(),
             props: vec![
                 ro("Style", "ml_style", self.style_name.clone()),
+                ro(
+                    "Style Handle",
+                    "ml_style_handle",
+                    match self.style_handle {
+                        Some(h) if !h.is_null() => format!("{:X}", h.value()),
+                        _ => "(none)".to_string(),
+                    },
+                ),
                 ro("Vertices", "ml_verts", self.vertices.len().to_string()),
+                ro(
+                    "Style Elements",
+                    "ml_style_elem_count",
+                    self.style_element_count.to_string(),
+                ),
                 edit("Scale", "ml_scale", self.scale_factor),
+                Property {
+                    label: "Justification".into(),
+                    field: "ml_justification",
+                    value: PropValue::Choice {
+                        selected: just_str.to_string(),
+                        options: ["Top", "Zero", "Bottom"]
+                            .into_iter()
+                            .map(str::to_string)
+                            .collect(),
+                    },
+                },
                 Property {
                     label: "Closed".into(),
                     field: "ml_closed",
@@ -186,6 +215,14 @@ impl PropertyEditable for MLine {
                     .set(acadrust::entities::MLineFlags::CLOSED, closed);
                 return;
             }
+            "ml_justification" => {
+                self.justification = match value {
+                    "Top" => acadrust::entities::MLineJustification::Top,
+                    "Bottom" => acadrust::entities::MLineJustification::Bottom,
+                    _ => acadrust::entities::MLineJustification::Zero,
+                };
+                return;
+            }
             _ => {}
         }
         let Ok(v) = value.trim().parse::<f64>() else {