feat(scene): render 3D surface entities (loft/sweep/extrude/etc.)

ACAD_SURFACE entities now load and render. Their NURBS faces are
tessellated by building a truck BSplineSurface from the ACIS `spline-surface`
control net and knot vectors, then sampling its parametric grid — reusing the
same NURBS kernel the Model tab already builds on. Analytic faces
(plane/cone/sphere/torus) continue through the existing tessellator.

- New spline_tess.rs: parse the ACIS `nubs` block (degrees, knots with the
  clamped end-multiplicity fix, control grid) into a truck BSplineSurface and
  mesh it.
- tessellate_surface + Surface wired through the mesh-build, fallback-wire,
  and entity-classification paths.
- Bump acadrust to the commit that adds the Surface entity.

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

Cargo.lock

@@ -56,7 +56,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.3.4"
-source = "git+https://github.com/HakanSeven12/acadrust?branch=main#b4ab9ffedfae44b5731301a94c849a3c8f695105"
+source = "git+https://github.com/HakanSeven12/acadrust?branch=main#3e2afad2d0baf03be584c28111040e13870b9e70"
 dependencies = [
  "ahash",
  "anyhow",
@@ -3178,7 +3178,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b577e2d69827c4740cba2b52efaad1c4cc7c73042860b199710b3575c68438d"
 dependencies = [
  "bytecount",
- "memchr 1.0.2",
+ "memchr 2.8.1",
  "nom 8.0.0",
 ]