feat: plinegen + SAB parsing for Solid3D/Region/Body

LwPolyline PLINEGEN=0 (DXF default): emit SegmentedLines with NaN
separators between vertex-to-vertex segments; wire_gpu resets
arc-length to 0 after each NaN so linetype pattern restarts per vertex.
PLINEGEN=1: existing Contour path unchanged (continuous pattern).
WireModel gains plinegen field propagated through tessellate pipeline.

Solid3D/Region/Body: call SabReader::read() when parse_sat() returns
None due to binary SAB format (DWG files / newer AutoCAD exports).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/home/draw/attdef.rs

@@ -134,6 +134,7 @@ impl CadCommand for AttdefCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/ellipse.rs

@@ -527,5 +527,6 @@ fn line_wire(from: Vec3, to: Vec3) -> WireModel {
         aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
     }
 }

src/modules/home/draw/line.rs

@@ -88,6 +88,7 @@ impl CadCommand for LineCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/mline.rs

@@ -113,6 +113,7 @@ impl CadCommand for MlineCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/raster_image.rs

@@ -112,6 +112,7 @@ impl CadCommand for ImageCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/ray.rs

@@ -86,6 +86,7 @@ impl CadCommand for RayCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }
@@ -164,6 +165,7 @@ impl CadCommand for XLineCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/revcloud.rs

@@ -83,6 +83,7 @@ impl CadCommand for RevCloudCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/draw/wipeout.rs

@@ -119,6 +119,7 @@ impl CadCommand for WipeoutCommand {
                     aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
                 })
             }
             WipeoutMode::Polygonal => {
@@ -140,6 +141,7 @@ impl CadCommand for WipeoutCommand {
                     aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
                 })
             }
         }

src/modules/home/inquiry/area.rs

@@ -76,6 +76,7 @@ impl CadCommand for AreaCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/inquiry/dist.rs

@@ -71,6 +71,7 @@ impl CadCommand for DistCommand {
             aci: 0,
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
         })
     }
 }

src/modules/home/modify/stretch.rs

@@ -134,6 +134,7 @@ impl CadCommand for StretchCommand {
                     aci: 0,
                     key_vertices: vec![],
                     aabb: WireModel::UNBOUNDED_AABB,
+            plinegen: true,
                 })
             }
             _ => None,