Feat: REVCLOUD command — revision cloud (arc-bumped closed polyline)

Pick polygon corners, Enter to close. Each edge is subdivided into arc
bumps (bulge = 0.5 ≈ 53° arcs). Result is a closed LwPolyline.
Arc bump length defaults to 1.0 drawing units.

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

src/modules/home/draw/mod.rs

@@ -7,5 +7,6 @@ pub mod line;
 pub mod point;
 pub mod polyline;
 pub mod ray;
+pub mod revcloud;
 pub mod shapes;
 pub mod spline;