Feat: Phase 4.3/4.4/4.5 — RasterImage, Wipeout, AttributeDefinition, AttributeEntity

- raster_image.rs: RasterImage renders as border rectangle + X diagonals
  (pixel placeholder); Wipeout renders border or polygon clip boundary;
  both support insertion_point grip, brightness/contrast/fade properties,
  clipping toggle, and mirror transform (u/v vectors reflected)
- attribute.rs: AttributeDefinition renders default_value (or [TAG] if
  empty) as font-tessellated text; AttributeEntity renders the live value;
  both support insertion grip, position/height/rotation properties,
  and transform operations
- mod.rs + traits.rs: wire up all four new entity types through the full
  dispatch chain (to_truck, grips, geometry_properties, apply_geom_prop,
  apply_grip, apply_transform)

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

src/entities/mod.rs

@@ -1,4 +1,5 @@
 pub mod arc;
+pub mod attribute;
 pub mod circle;
 mod common;
 pub mod dimension;
@@ -12,6 +13,7 @@ pub mod lwpolyline;
 pub mod mtext;
 pub mod point;
 pub mod polyline;
+pub mod raster_image;
 pub mod ray;
 pub mod spline;
 pub mod text;