feat: BOX, SPHERE, CYLINDER primitives + EXTRUDE / REVOLVE commands

BOX, SPHERE, and CYLINDER build truck topology solids and tessellate
them into MeshModels stored alongside a Solid3D placeholder entity so
the GPU mesh pipeline renders them immediately.

EXTRUDE picks any closed 2D profile (Circle, LwPolyline, etc.),
attaches a planar face via try_attach_plane, and translational-sweeps
it (tsweep Face → Solid) along Z by the given height.

REVOLVE picks a profile, two axis points, and an angle (default 360°),
then rotational-sweeps the wire (rsweep) around the axis.

Three new CmdResult variants drive the operations:
  CommitSolid3D, ExtrudeEntity, RevolveEntity.

Scene::layer_color() added to retrieve the active layer's RGBA color.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

ROADMAP.md

@@ -293,7 +293,8 @@ Underlay (PDF/DWF/DGN)
 | OBJ mesh içe aktarma | ✅ |
 | Solid3D tessellation (acadrust ACIS) | ✅ |
 | Boolean operasyonlar (UNION/SUBTRACT/INTERSECT) | ⬜ |
-| EXTRUDE / REVOLVE / SWEEP / LOFT | ⬜ |
+| EXTRUDE / REVOLVE | ✅ |
+| SWEEP / LOFT | ⬜ |
 | 3D ARRAY | ✅ |
 | STL dışa aktarma (STLOUT) | ✅ |
 | STEP dışa aktarma | ⬜ |