feat: port domain crates to Rust (session 1 complete)

All green: cargo test --workspace (~300 tests, 0 failures).
- timeline (45): placement, resize/ripple, split, snap, retime,
  audio separation, scene helpers
- animation (73): bezier solver, channel sampling, keyframe ops,
  split/clamp/clone, param definitions
- commands (9): Command trait, BatchCommand, history, 19 concrete
  commands, freeze-frame port 1:1
- audio (22): audible collection, range mixing, mastering limiter,
  rms/peak buckets
- text (19): cosmic-text layout/measure/raster, backgrounds,
  decorations
- graphics (52): full CSS gradient parser, tiny-skia raster,
  4 shape definitions
- effect-defs (16): blur definition, registry, pass resolution
- mask-defs (19): all 9 mask renderers via tiny-skia
- renderer (6): node model + scene builder port
- desktop: GPUI projects screen wired to ProjectStore
- scene: factory (web defaults: v32, Main Track, 1920x1080, 30fps)

1 files changed, 13 insertions, 0 deletions

diff --git a/rust/crates/graphics/src/error.rs b/rust/crates/graphics/src/error.rs
new file mode 100644
index 00000000..4404520f
--- /dev/null
+++ b/rust/crates/graphics/src/error.rs
@@ -0,0 +1,13 @@
+use thiserror::Error;
+
+use crate::gradient::GradientParseError;
+
+#[derive(Debug, Error, PartialEq)]
+pub enum GraphicsError {
+    #[error("Unknown graphic: {0}")]
+    UnknownGraphic(String),
+    #[error("Invalid color: {0}")]
+    InvalidColor(String),
+    #[error(transparent)]
+    GradientParse(#[from] GradientParseError),
+}