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/job/mod.rs

@@ -0,0 +1,140 @@
+//! CPU product-image work and its device-independent, session-scoped protocol.
+//! Hosts own execution; documents and history never contain these values.
+
+use std::fmt;
+use std::sync::{
+    Arc,
+    atomic::{AtomicBool, Ordering},
+};
+
+use serde::{Deserialize, Serialize};
+
+use crate::{BackendId, Camera, ExecutorId};
+
+mod host;
+mod image;
+pub use host::{CpuHost, HostKind, JobHandle, JobStatus, RenderFrame};
+pub use image::{Admission, ImageTask, TaskPoll, admit};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct JobId {
+    pub session: u64,
+    pub serial: u64,
+    pub generation: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum Phase {
+    Queued,
+    Preparing,
+    Running,
+    Encoding,
+    Cancelling,
+    Cancelled,
+    Completed,
+    Failed,
+}
+
+impl Phase {
+    pub fn terminal(self) -> bool {
+        matches!(self, Self::Cancelled | Self::Completed | Self::Failed)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize)]
+pub struct Progress {
+    pub phase: Phase,
+    pub done: u64,
+    pub total: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum ErrorCode {
+    InvalidRequest,
+    LimitExceeded,
+    AllocationFailed,
+    HostUnavailable,
+    QueueFull,
+    TimedOut,
+    Cancelled,
+    InvalidScene,
+    EncodingFailed,
+    WrongOwner,
+    UnknownJob,
+    NotCompleted,
+    Internal,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
+pub struct JobError {
+    pub code: ErrorCode,
+    pub message: String,
+}
+
+impl JobError {
+    pub fn new(code: ErrorCode, message: impl Into<String>) -> Self {
+        Self { code, message: message.into() }
+    }
+}
+
+impl fmt::Display for JobError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}: {}", self.code, self.message)
+    }
+}
+impl std::error::Error for JobError {}
+
+pub type Result<T> = std::result::Result<T, JobError>;
+
+#[derive(Clone, Default)]
+pub struct CancelToken(Arc<AtomicBool>);
+
+impl CancelToken {
+    pub fn cancel(&self) {
+        self.0.store(true, Ordering::Release);
+    }
+    pub fn is_cancelled(&self) -> bool {
+        self.0.load(Ordering::Acquire)
+    }
+    pub fn check(&self) -> Result<()> {
+        if self.is_cancelled() { Err(JobError::new(ErrorCode::Cancelled, "render cancelled")) } else { Ok(()) }
+    }
+}
+
+/// Fully resolved input; no mutable session, topology graph or GPU resources.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct ImageRequest {
+    pub camera: Camera,
+    pub width: u32,
+    pub height: u32,
+    pub background: [u8; 3],
+    pub transparent_background: bool,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum ColourEncoding {
+    Srgb,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum AlphaConvention {
+    Straight,
+}
+
+#[derive(Clone, Debug, Serialize)]
+pub struct FrameInfo {
+    pub job: JobId,
+    pub scene_generation: u64,
+    pub backend: BackendId,
+    pub executor: ExecutorId,
+    pub width: u32,
+    pub height: u32,
+    pub encoding: ColourEncoding,
+    pub alpha: AlphaConvention,
+}