Implement the reviewed UI icon system and durable review workflow (#853)

Thanks @Nathan-Dane.

crates/engine/src/cmd/sketch_3d.rs

@@ -12,17 +12,20 @@ use crate::params::{bad, req_vec3, vec3};
 use crate::{Result, Session};
 
 pub static COMMANDS: &[CommandSpec] = &[
-    CommandSpec::new("sketch.line3d", "3D Line", line3d).enabled(in_sketch).params(concat!(
+    CommandSpec::new("sketch.line3d", "3D Line", line3d).icon("line").enabled(in_sketch).params(concat!(
         "points: [[x,y,z]…] world points (2 or more): one 3D line per segment, joined end to end (needs 3D Sketch on)",
         created_doc!()
     )),
     CommandSpec::new("sketch.spline3d", "3D Spline", spline3d)
+        .icon("spline")
         .enabled(in_sketch)
         .params(concat!("points: [[x,y,z]…] world fit points (2 or more): a smooth 3D curve through them (needs 3D Sketch on)", created_doc!())),
     CommandSpec::new("sketch.point3d", "3D Point", point3d)
+        .icon("point")
         .enabled(in_sketch)
         .params(concat!("point: [x,y,z] world point (needs 3D Sketch on)", created_doc!())),
     CommandSpec::new("sketch.move3d", "Move 3D Point", move3d)
+        .icon("sketch_move")
         .enabled(in_sketch)
         .params("wire: drawn 3D curve or point id, index?: fit point (default 0), to: [x,y,z] | by: [dx,dy,dz]; points joined to it move too"),
 ];