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/render/src/product.rs

@@ -0,0 +1,42 @@
+//! Renderer-independent product geometry. No modelling overlays or device resources.
+
+use std::sync::Arc;
+
+use solidcraft_geom::{Aabb3, Mesh};
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct FaceAppearance {
+    /// The existing mesh's B-rep face index, resolved by the document's appearance policy.
+    pub face: u32,
+    pub color: [u8; 3],
+    pub opacity: f64,
+    pub surface: Option<crate::surface::OpaqueSurface>,
+}
+
+#[derive(Clone, Debug)]
+pub struct ProductMesh {
+    /// Existing computed body name, including occurrence identity where applicable.
+    pub name: String,
+    /// Established world-space mesh. Adapters must not apply occurrence transforms again.
+    pub mesh: Arc<Mesh>,
+    pub color: [u8; 3],
+    pub opacity: f64,
+    pub surface: Option<crate::surface::OpaqueSurface>,
+    pub faces: Vec<FaceAppearance>,
+}
+
+#[derive(Clone, Debug)]
+pub struct ProductScene {
+    pub meshes: Vec<ProductMesh>,
+    pub bounds: Aabb3,
+}
+
+impl ProductScene {
+    pub fn required_features(&self) -> Vec<crate::RenderFeature> {
+        if self.meshes.iter().any(|m| m.surface.is_some() || m.faces.iter().any(|f| f.surface.is_some())) {
+            vec![crate::RenderFeature::Pbr]
+        } else {
+            Vec::new()
+        }
+    }
+}