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, 87 insertions, 0 deletions

diff --git a/rust/crates/mask-defs/src/freeform.rs b/rust/crates/mask-defs/src/freeform.rs
new file mode 100644
index 00000000..6c464977
--- /dev/null
+++ b/rust/crates/mask-defs/src/freeform.rs
@@ -0,0 +1,87 @@
+use scene::FreeformPathPoint;
+use tiny_skia::{Path, PathBuilder};
+
+fn local_to_canvas(
+    x: f64,
+    y: f64,
+    center_x: f64,
+    center_y: f64,
+    rotation: f64,
+    scale: f64,
+    width: f64,
+    height: f64,
+) -> (f64, f64) {
+    let canvas_center_x = width / 2.0 + center_x * width;
+    let canvas_center_y = height / 2.0 + center_y * height;
+    let scaled_x = x * width * scale;
+    let scaled_y = y * height * scale;
+    let angle_rad = rotation.to_radians();
+    let cos = angle_rad.cos();
+    let sin = angle_rad.sin();
+    (
+        canvas_center_x + scaled_x * cos - scaled_y * sin,
+        canvas_center_y + scaled_x * sin + scaled_y * cos,
+    )
+}
+
+#[allow(clippy::too_many_arguments)]
+pub fn build_freeform_path(
+    points: &[FreeformPathPoint],
+    center_x: f64,
+    center_y: f64,
+    rotation: f64,
+    scale: f64,
+    width: f64,
+    height: f64,
+    closed: bool,
+) -> Option<Path> {
+    if points.is_empty() {
+        return None;
+    }
+
+    let to_canvas = |x: f64, y: f64| {
+        local_to_canvas(x, y, center_x, center_y, rotation, scale, width, height)
+    };
+
+    let anchors: Vec<((f64, f64), (f64, f64), (f64, f64))> = points
+        .iter()
+        .map(|point| {
+            (
+                to_canvas(point.x, point.y),
+                to_canvas(point.x + point.in_x, point.y + point.in_y),
+                to_canvas(point.x + point.out_x, point.y + point.out_y),
+            )
+        })
+        .collect();
+
+    let mut builder = PathBuilder::new();
+    builder.move_to(anchors[0].0 .0 as f32, anchors[0].0 .1 as f32);
+    for index in 1..anchors.len() {
+        let previous = anchors[index - 1];
+        let current = anchors[index];
+        builder.cubic_to(
+            previous.2 .0 as f32,
+            previous.2 .1 as f32,
+            current.1 .0 as f32,
+            current.1 .1 as f32,
+            current.0 .0 as f32,
+            current.0 .1 as f32,
+        );
+    }
+
+    if closed && anchors.len() > 1 {
+        let last = anchors[anchors.len() - 1];
+        let first = anchors[0];
+        builder.cubic_to(
+            last.2 .0 as f32,
+            last.2 .1 as f32,
+            first.1 .0 as f32,
+            first.1 .1 as f32,
+            first.0 .0 as f32,
+            first.0 .1 as f32,
+        );
+        builder.close();
+    }
+
+    builder.finish()
+}