ocs_doc_api: Phase 3-ii — typed AttributeDefinition create (Phase 3 complete)

- CreateAttributeDefinition(AttributeDefinitionSpec) op (append-only).
- backend add_attribute_definition (ATTDEF tag/prompt/default/insertion/height/rotation).
- facade create_attribute_definition; entity_kind_name AttributeDefinition/AttributeEntity.
- spec AttributeDefinition family; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase3ii_create_attribute_definition -> 614 host lib + 3 consistency green.

crates/ocs_doc_api/src/executor.rs

@@ -287,6 +287,12 @@ pub fn apply_op<B: DocApiBackend>(b: &mut B, op: Operation) -> ApiResult<Receipt
             b.finalize_op();
             OpOutcome::NewId(id)
         }
+        Operation::CreateAttributeDefinition(spec) => {
+            b.push_undo(name);
+            let id = b.add_attribute_definition(spec)?;
+            b.finalize_op();
+            OpOutcome::NewId(id)
+        }
     };
     Ok(Receipt {
         outcome: Some(outcome),