ocs_doc_api: Phase 2c-iii — 2-line angular dimension (all dimension sub-types done)

- CreateDimensionAngular2Ln(DimensionAngularSpec) op (append-only).
- backend add_dimension_angular2ln (DimensionAngular2Ln::new computes angle).
- facade create_dimension_angular2ln; spec constructor; api_reference + binding_schema
  regenerated; mocks + baseline.
- IMPLEMENTATION.md: fix stale Status line (all 5 phases complete, current test
  counts); mark all dimension sub-types done.
- Test phase2ciii_dimension_angular2ln (90-degree 2-line angle) -> 616 host lib +
  3 consistency green.

crates/ocs_doc_api/src/backend.rs

@@ -78,6 +78,9 @@ pub trait DocApiBackend {
     /// Add a `TABLE` (rows × columns grid); returns the fresh `ObjectId`.
     fn add_table(&mut self, spec: &crate::ops::TableSpec) -> ApiResult<ObjectId>;
 
+    /// Add a 2-line angular `DIMENSION`; returns the fresh `ObjectId`.
+    fn add_dimension_angular2ln(&mut self, spec: &crate::ops::DimensionAngularSpec) -> ApiResult<ObjectId>;
+
     /// A dimension's measured value (distance for linear/radius, degrees for angular).
     fn dimension_measurement(&self, id: ObjectId) -> ApiResult<f64>;
 

crates/ocs_doc_api/src/executor.rs

@@ -304,6 +304,12 @@ pub fn apply_op<B: DocApiBackend>(b: &mut B, op: Operation) -> ApiResult<Receipt
             b.finalize_op();
             OpOutcome::NewId(id)
         }
+        Operation::CreateDimensionAngular2Ln(spec) => {
+            b.push_undo(name);
+            let id = b.add_dimension_angular2ln(spec)?;
+            b.finalize_op();
+            OpOutcome::NewId(id)
+        }
     };
     Ok(Receipt {
         outcome: Some(outcome),

crates/ocs_doc_api/src/facade.rs

@@ -539,6 +539,14 @@ impl CurveCollection {
         Ok(Entity::new(self.session.clone(), id))
     }
 
+    /// A 2-line angular DIMENSION: angle between lines (vertex→first) and (vertex→second).
+    pub fn create_dimension_angular2ln(&self, vertex: [f64; 3], first_point: [f64; 3], second_point: [f64; 3], arc_location: [f64; 3]) -> ApiResult<Dimension> {
+        let receipt = self.session.apply_op(Operation::CreateDimensionAngular2Ln(crate::ops::DimensionAngularSpec {
+            vertex, first_point, second_point, arc_location,
+        }))?;
+        let id = receipt.outcome.and_then(|o| o.new_id()).ok_or_else(|| ApiError::Transport("create_dimension returned no id".into()))?;
+        Ok(Dimension::new(self.session.clone(), id))
+    }
     /// A radial DIMENSION for the circle centered at `center` through `point`.
     pub fn create_dimension_radius(&self, center: [f64; 3], point: [f64; 3]) -> ApiResult<Dimension> {
         self.create_dim_radial(Operation::CreateDimensionRadius, center, point)

crates/ocs_doc_api/src/gen/api_reference.md

@@ -136,6 +136,7 @@ Linear dimension between two measured points. measurement() reads the distance;
 - **create_dimension_radius**(center: [f64; 3], point: [f64; 3]) -> `Dimension` — `CreateDimensionRadius`
 - **create_dimension_diameter**(center: [f64; 3], point: [f64; 3]) -> `Dimension` — `CreateDimensionDiameter`
 - **create_dimension_angular**(vertex: [f64; 3], first_point: [f64; 3], second_point: [f64; 3], arc_location: [f64; 3]) -> `Dimension` — `CreateDimensionAngular`
+- **create_dimension_angular2ln**(vertex: [f64; 3], first_point: [f64; 3], second_point: [f64; 3], arc_location: [f64; 3]) -> `Dimension` — `CreateDimensionAngular2Ln`
 
 ### Methods
 

crates/ocs_doc_api/src/gen/ops_gen.rs

@@ -56,4 +56,6 @@ pub enum Operation {
     CreateAttributeDefinition(AttributeDefinitionSpec),
     // tables
     CreateTable(TableSpec),
+    // dimension sub-types (2-line angular)
+    CreateDimensionAngular2Ln(DimensionAngularSpec),
 }

crates/ocs_doc_api/src/ops.rs

@@ -233,6 +233,7 @@ impl crate::gen::Operation {
             CreateDimensionAngular(_) => "CreateDimensionAngular",
             CreateAttributeDefinition(_) => "CreateAttributeDefinition",
             CreateTable(_) => "CreateTable",
+            CreateDimensionAngular2Ln(_) => "CreateDimensionAngular2Ln",
         }
     }
 }