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/gen/api_reference.md

@@ -158,6 +158,11 @@ Paper-space viewport: a width×height window at center looking at view_target wi
 
 - **create_viewport**(`center: [f64; 3], width: f64, height: f64, view_target: [f64; 3], view_height: f64`) -> `Entity`
 
+### Methods
+
+- **viewport_view**(``) -> `([f64; 3], f64)` — query `GetViewportView`
+- **set_view**(`view_target: [f64; 3], view_height: f64`) -> `()` — op `SetViewportView`
+
 ## `Entity` (acadrust `RasterImage`, collection `entities`)
 
 Raster image (read-mostly): GetEntity kind + coarse bounds (insertion + u*width + v*height); generic delete. No typed create in v1.