ocs_doc_api: Phase 4 set_view + viewport-view query

- SetViewportView op + GetViewportView query (append-only).
- backend set_viewport_view (update Viewport.view_target/view_height) + viewport_view.
- facade Entity::set_view/viewport_view (Viewport returns Entity).
- spec Viewport methods; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase4_set_view_and_view_query -> 609 host lib + 3 consistency green.
- Phase 4 complete.

crates/ocs_doc_api/src/ops.rs

@@ -170,6 +170,7 @@ impl crate::gen::Operation {
             CreateHatch(_) => "CreateHatch",
             CreateDimensionLinear(_) => "CreateDimensionLinear",
             SetAttribute { .. } => "SetAttribute",
+            SetViewportView { .. } => "SetViewportView",
         }
     }
 }