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/src/backend.rs

@@ -84,6 +84,10 @@ pub trait DocApiBackend {
     /// Add a `RASTER_IMAGE` (host auto-registers the ImageDefinition).
     fn add_raster_image(&mut self, spec: &crate::ops::RasterImageSpec) -> ApiResult<ObjectId>;
 
+    /// Loft a solid through >= 2 profile curve sets (each already resolved to
+    /// `geom2d::Curve`s on the XY plane). Returns the fresh `ObjectId`.
+    fn loft(&mut self, sections: &[Vec<cadkernel::geom2d::Curve>]) -> ApiResult<ObjectId>;
+
     /// Can `id` be modified in place right now (exists, is the expected family,
     /// not on a locked layer)? Read-only pre-check used before mutations.
     /// Default: existence + not-locked (backends narrow the family check).

crates/ocs_doc_api/src/executor.rs

@@ -253,6 +253,22 @@ pub fn apply_op<B: DocApiBackend>(b: &mut B, op: Operation) -> ApiResult<Receipt
             b.finalize_op();
             OpOutcome::NewId(id)
         }
+        Operation::Loft { profiles } => {
+            // Resolve every profile to its curve set BEFORE push_undo (all-or-nothing).
+            if profiles.len() < 2 {
+                return Err(ApiError::validation(name, "loft needs >= 2 profiles"));
+            }
+            let mut sections = Vec::with_capacity(profiles.len());
+            for (i, p) in profiles.iter().enumerate() {
+                let curves = profile_curves(b, *p, name)
+                    .map_err(|e| at_index(name, i, e))?;
+                sections.push(curves);
+            }
+            b.push_undo(name);
+            let id = b.loft(&sections)?;
+            b.finalize_op();
+            OpOutcome::NewId(id)
+        }
     };
     Ok(Receipt {
         outcome: Some(outcome),

crates/ocs_doc_api/src/facade.rs

@@ -452,6 +452,13 @@ impl SolidCollection {
             .ok_or_else(|| ApiError::Transport("revolve returned no id".into()))?;
         Ok(Solid::new(self.session.clone(), id))
     }
+    /// Loft a solid through >= 2 profile entities (polylines/circles/arcs).
+    pub fn loft(&self, profiles: &[impl HasId]) -> ApiResult<Solid> {
+        let ids: Vec<ObjectId> = profiles.iter().map(|p| p.id()).collect();
+        let receipt = self.session.apply_op(Operation::Loft { profiles: ids })?;
+        let id = receipt.outcome.and_then(|o| o.new_id()).ok_or_else(|| ApiError::Transport("loft returned no id".into()))?;
+        Ok(Solid::new(self.session.clone(), id))
+    }
 }
 
 #[derive(Clone)]

crates/ocs_doc_api/src/gen/api_reference.md

@@ -18,6 +18,7 @@ B-rep solid. Host resolves bodies via the solid_models cache (lift-on-miss from
 - **create_wedge**(`origin: [f64; 3], size: [f64; 3]`) -> `Solid`
 - **extrude**(`profile: EntityRef, direction: [f64; 3]`) -> `Solid`
 - **revolve**(`profile: EntityRef, pivot: [f64; 3], axis: [f64; 3], angle: f64`) -> `Solid`
+- **loft**(`profiles: &[EntityRef]`) -> `Solid`
 
 ### Methods
 

crates/ocs_doc_api/src/gen/ops_gen.rs

@@ -46,4 +46,6 @@ pub enum Operation {
     SetViewportView { id: ObjectId, view_target: [f64; 3], view_height: f64 },
     // media
     CreateRasterImage(RasterImageSpec),
+    // multi-profile solid
+    Loft { profiles: Vec<ObjectId> },
 }

crates/ocs_doc_api/src/ops.rs

@@ -185,6 +185,7 @@ impl crate::gen::Operation {
             SetAttribute { .. } => "SetAttribute",
             SetViewportView { .. } => "SetViewportView",
             CreateRasterImage(_) => "CreateRasterImage",
+            Loft { .. } => "Loft",
         }
     }
 }