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/spec/entities.toml

@@ -237,6 +237,21 @@ args = [{ name = "origin", ty = "[f64; 3]" }, { name = "direction", ty = "[f64;
 op = "CreateCurve"
 fixed = { curve = "XLine" }
 
+# ============================================================================
+# CONTAINER FAMILY (phase 3) — block references
+# ============================================================================
+[[family]]
+name = "Insert"
+acadrust_variant = "Insert"
+handle = "Entity"
+collection = "entities"
+description = "Block reference. Place an existing BlockRecord by name; transform moves its insert point."
+
+[[family.constructor]]
+name = "create_insert"
+args = [{ name = "block_name", ty = "&str" }, { name = "insert_point", ty = "[f64; 3]" }, { name = "scale", ty = "f64" }, { name = "rotation", ty = "f64" }]
+op = "CreateInsert"
+
 # ============================================================================
 # Cross-cutting ops (generic handles + bulk) — documented in build.rs
 # ============================================================================