Render: integrated workspace, preview image jobs and opaque PBR (#1046)

Lands the Render workspace (R3), bounded preview-image jobs with cancellation and atomic PNG export (R4a), and opaque PBR looks as one change.

- Render workspace: an overlay-free product preview on the installed GPU device. Returning to Design restores its camera. render.scene and render.settings.apply are added.
- Image jobs: render.preflight/start/status/cancel/export run bounded CPU preview jobs. Export captures the job, overwrite choice and document, and checks the caller's file scope before writing.
- Opaque PBR: looks can carry metal fraction, roughness and dielectric IOR. The product viewport and preview PNG use them; geometry and mass are unchanged. The v1 catalog export refuses PBR rather than dropping it.
- Render setups and PBR looks are saved under design format 21. Labels are in en/de/ja/ko/zh/ru.

Supersedes #706 and #800. Refs #620, #673, #756, #1004.

Contributed by @0xlillith.

Co-authored-by: lillith <35337584+0xlillith@users.noreply.github.com>

crates/engine/src/cmd/component_transfer_tests.rs

@@ -159,7 +159,10 @@ fn inherited_component_appearance_and_legacy_assignment_survive_transfer() {
     let mut s = Session::default();
     let source = run(&mut s, "component.create", json!({"name":"Source"}))["component"].as_u64().unwrap();
     run(&mut s, "solid.box", json!({"length":10,"width":10,"height":10,"body_name":"Block"}));
-    s.doc_mut().appearances.components.insert(source, solidcraft_doc::appearance::Look { name: "Green".into(), color: [0, 150, 0], opacity: 0.7 });
+    s.doc_mut()
+        .appearances
+        .components
+        .insert(source, solidcraft_doc::appearance::Look { name: "Green".into(), color: [0, 150, 0], opacity: 0.7, pbr: None });
     s.refresh();
     let look = s.doc.model_body_look(s.model.state().body("Block").unwrap()).unwrap();
     run(&mut s, "component.move_bodies", json!({"component":0,"bodies":["Block"]}));