ocs_doc_api: outstanding methods — loft + bulge-arc polyline profiles

- Loft{profiles} op (append-only); executor resolves each profile to curve sets
  all-or-nothing; backend loft() -> brep::loft on XY plane; facade solids().loft.
- entity_to_profile_curves: convert LwVertex.bulge to geom2d::Curve::Arc via
  bulge_arc_segment (theta = 4*atan(bulge)), so bulged polyline profiles sweep
  correctly instead of erroring Unsupported.
- spec loft; api_reference + binding_schema regenerated; mocks + baseline.
- Tests: loft_two_profiles_produces_solid, bulge_arc_polyline_profile_converts_to_arc
  (semicircle radius=5 for bulge=1) -> 612 host lib + 3 consistency green.

crates/ocs_doc_api/tests/mock_backend.rs

@@ -147,6 +147,15 @@ impl DocApiBackend for MockBackend {
     fn add_raster_image(&mut self, _spec: &ocs_doc_api::ops::RasterImageSpec) -> ApiResult<ObjectId> {
         Ok(self.alloc("RasterImage"))
     }
+    fn loft(&mut self, sections: &[Vec<cadkernel::geom2d::Curve>]) -> ApiResult<ObjectId> {
+        if sections.len() < 2 {
+            return Err(ApiError::validation("Loft", "loft needs >= 2 profiles"));
+        }
+        // Mock: store a unit cuboid as the loft result.
+        let body = cadkernel::brep::make::cuboid([0.0, 0.0, 0.0], [1.0; 3])
+            .ok_or_else(|| ApiError::geometry(GeometryErrorKind::InvalidInput, "make cuboid"))?;
+        self.store_solid(&body)
+    }
     fn set_viewport_view(&mut self, id: ObjectId, view_target: [f64; 3], view_height: f64) -> ApiResult<()> {
         if !self.entity_exists(id) {
             return Err(ApiError::UnknownId(id));

crates/ocs_doc_api/tests/spec_wire_consistency.rs

@@ -63,6 +63,7 @@ fn operation_variants() -> Vec<String> {
         Operation::CreateRasterImage(ocs_doc_api::ops::RasterImageSpec {
             file_path: String::new(), insertion_point: [0.0; 3], u_vector: [0.0; 3], v_vector: [0.0; 3], size: [0.0; 2],
         }),
+        Operation::Loft { profiles: vec![] },
     ];
     // Derive the variant names by serializing a probe of each and reading the
     // bincode variant index -> name map is not available; instead match by
@@ -151,6 +152,7 @@ const OPERATION_BASELINE: &[&str] = &[
     "SetAttribute",
     "SetViewportView",
     "CreateRasterImage",
+    "Loft",
 ];
 
 /// Recorded baseline of the `Query` variant order.