fix(mirror): negate polyline bulges in the MIRROR command

The MIRROR command's LwPolyline / Polyline2D closures reflected the
vertices but left the bulges untouched, so every curved segment of a
mirrored polyline bowed to the wrong side. A reflection reverses the
side a bulge arc bows to — negate it alongside the vertex reflection
(same convention acadrust applies on its reflecting-transform paths).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/entities/lwpolyline.rs

@@ -421,6 +421,9 @@ fn apply_transform(pline: &mut LwPolyline, t: &EntityTransform) {
     crate::scene::transform::apply_standard_entity_transform(pline, t, |entity, p1, p2| {
         for v in &mut entity.vertices {
             crate::scene::transform::reflect_xy_point(&mut v.location.x, &mut v.location.y, p1, p2);
+            // Bulge encodes which side the arc bows to; a reflection
+            // reverses it or every curved segment flips to the wrong side.
+            v.bulge = -v.bulge;
         }
     });
 }

src/entities/polyline.rs

@@ -475,6 +475,9 @@ impl Transformable for Polyline2D {
                     p1,
                     p2,
                 );
+                // Bulge encodes which side the arc bows to; a reflection
+                // reverses it or every curved segment flips to the wrong side.
+                v.bulge = -v.bulge;
             }
         });
     }