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, 15 insertions, 0 deletions

diff --git a/rust/crates/graphics/src/gradient/mod.rs b/rust/crates/graphics/src/gradient/mod.rs
new file mode 100644
index 00000000..ec597ad0
--- /dev/null
+++ b/rust/crates/graphics/src/gradient/mod.rs
@@ -0,0 +1,15 @@
+pub mod ast;
+pub mod parser;
+pub mod raster;
+pub mod stops;
+
+pub use ast::{
+    Color, ColorStop, Distance, GradientAst, GradientKind, GradientOrientation,
+    LinearOrientation, Position, RadialOrientation, Shape, ShapeKind, ShapeStyle,
+};
+pub use parser::{GradientParseError, parse_gradient};
+pub use raster::{
+    BackgroundLayer, draw_css_background, is_gradient_layer, parse_background_layers,
+    split_css_layers,
+};
+pub use stops::{NormalizedColorStop, color_to_string, normalize_color_stops};