ocs_doc_api: Phase 3 (block references)

- Operation::CreateInsert(InsertSpec) appended to the wire enum (append-only).
- backend add_insert validates the BlockRecord exists (unknown block -> Validation,
  no mutation); host inserts acadrust::entities::Insert with scale+rotation.
- Insert transform moves insert_point (transform_entity_geometry) +
  ensure_transformable includes Insert.
- facade EntityCollection::create_insert; spec Insert family; api_reference +
  binding_schema regenerated; mocks updated.
- Test phase3_create_insert_and_transform -> 599 host lib green.
- IMPLEMENTATION.md: Phase 3 done (attributes/traversal remaining).

crates/ocs_doc_api/src/gen/api_reference.md

@@ -87,6 +87,14 @@ B-rep solid. Host resolves bodies via the solid_models cache (lift-on-miss from
 
 - **create_xline**(`origin: [f64; 3], direction: [f64; 3]`) -> `XLine`
 
+## `Entity` (acadrust `Insert`, collection `entities`)
+
+Block reference. Place an existing BlockRecord by name; transform moves its insert point.
+
+### Constructors (`doc.entities()`)
+
+- **create_insert**(`block_name: &str, insert_point: [f64; 3], scale: f64, rotation: f64`) -> `Entity`
+
 ## Generic methods (every handle)
 
 Every typed handle (`Solid`, `Line`, `Circle`, `Polyline`, `Point`, `Entity`) is a

crates/ocs_doc_api/src/gen/binding_schema.json

@@ -187,6 +187,13 @@
       "handle": "XLine",
       "methods": [],
       "name": "XLine"
+    },
+    {
+      "acadrust_variant": "Insert",
+      "collection": "entities",
+      "handle": "Entity",
+      "methods": [],
+      "name": "Insert"
     }
   ],
   "layouts": {

crates/ocs_doc_api/src/gen/ops_gen.rs

@@ -6,7 +6,7 @@
 use serde::{Deserialize, Serialize};
 
 use crate::id::ObjectId;
-use crate::ops::{BoolOp, Curve2Spec, EntitySpec, PlacementSpec, SolidPrimitive};
+use crate::ops::{BoolOp, Curve2Spec, EntitySpec, InsertSpec, PlacementSpec, SolidPrimitive};
 
 /// A typed write operation (plan §5). Each variant is ONE atomic host call = one
 /// undo step. Append new variants at the END only.
@@ -27,4 +27,6 @@ pub enum Operation {
     CreateMany(Vec<EntitySpec>),
     TransformMany { ids: Vec<ObjectId>, placement: PlacementSpec },
     DeleteMany(Vec<ObjectId>),
+    // containers
+    CreateInsert(InsertSpec),
 }