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, 62 insertions, 0 deletions

diff --git a/apps/desktop/src/app.rs b/apps/desktop/src/app.rs
new file mode 100644
index 00000000..8eab4f87
--- /dev/null
+++ b/apps/desktop/src/app.rs
@@ -0,0 +1,62 @@
+use gpui::{Context, Window, div, prelude::*, rgb};
+
+use crate::projects_view::ProjectsView;
+use crate::theme;
+
+pub enum Screen {
+    Projects,
+    Editor { project_id: String, project_name: String },
+}
+
+pub struct OpenCutApp {
+    pub screen: Screen,
+    pub projects_view: gpui::Entity<ProjectsView>,
+}
+
+impl OpenCutApp {
+    pub fn new(cx: &mut Context<Self>) -> Self {
+        let app = cx.weak_entity();
+        let projects_view = cx.new(|_| ProjectsView::new(app));
+        Self {
+            screen: Screen::Projects,
+            projects_view,
+        }
+    }
+
+    pub fn open_project(&mut self, project_id: String, project_name: String, cx: &mut Context<Self>) {
+        self.screen = Screen::Editor {
+            project_id,
+            project_name,
+        };
+        cx.notify();
+    }
+}
+
+impl Render for OpenCutApp {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        let content: gpui::AnyElement = match &self.screen {
+            Screen::Projects => self.projects_view.clone().into_any_element(),
+            Screen::Editor { project_name, project_id } => div()
+                .size_full()
+                .flex()
+                .flex_col()
+                .items_center()
+                .justify_center()
+                .gap_2()
+                .child(format!("Editing: {project_name}"))
+                .child(
+                    div()
+                        .text_sm()
+                        .text_color(rgb(theme::TEXT_SECONDARY))
+                        .child(format!("Editor UI lands here — preview, timeline, panels ({project_id})")),
+                )
+                .into_any_element(),
+        };
+
+        div()
+            .size_full()
+            .bg(rgb(theme::BACKGROUND))
+            .text_color(rgb(theme::TEXT_PRIMARY))
+            .child(content)
+    }
+}