feat: GPUI desktop port foundation

- scene crate: full project/scene/element model, serde round-trip
  proven against the web SerializedProject shape
- transfer crate: .ocp zip container, cross-compat with web fflate
  archives proven in both directions
- storage crate: filesystem project store replacing IndexedDB,
  .ocp import/export
- media crate: ffmpeg-next 8 decoder (frames, audio, thumbnails,
  waveform summaries)
- playback crate: wall-clock anchored, frame-rounded playback clock
- gpu crate: native texture readback; compositor renders headless
  offscreen on Vulkan (spike test)
- flake devshell: rust toolchain, GPUI native deps, ffmpeg dev,
  bindgen clang args; GPUI hello-world builds
- port plan in notes/gpui-port.md

1 files changed, 88 insertions, 0 deletions

diff --git a/rust/crates/scene/src/track.rs b/rust/crates/scene/src/track.rs
new file mode 100644
index 00000000..b35a7b25
--- /dev/null
+++ b/rust/crates/scene/src/track.rs
@@ -0,0 +1,88 @@
+use serde::{Deserialize, Serialize};
+
+use crate::element::Element;
+
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
+#[serde(tag = "type", rename_all = "camelCase")]
+pub enum Track {
+    Video {
+        id: String,
+        name: String,
+        elements: Vec<Element>,
+        muted: bool,
+        hidden: bool,
+    },
+    Text {
+        id: String,
+        name: String,
+        elements: Vec<Element>,
+        hidden: bool,
+    },
+    Audio {
+        id: String,
+        name: String,
+        elements: Vec<Element>,
+        muted: bool,
+    },
+    Graphic {
+        id: String,
+        name: String,
+        elements: Vec<Element>,
+        hidden: bool,
+    },
+    Effect {
+        id: String,
+        name: String,
+        elements: Vec<Element>,
+        hidden: bool,
+    },
+}
+
+impl Track {
+    pub fn id(&self) -> &str {
+        match self {
+            Track::Video { id, .. }
+            | Track::Text { id, .. }
+            | Track::Audio { id, .. }
+            | Track::Graphic { id, .. }
+            | Track::Effect { id, .. } => id,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        match self {
+            Track::Video { name, .. }
+            | Track::Text { name, .. }
+            | Track::Audio { name, .. }
+            | Track::Graphic { name, .. }
+            | Track::Effect { name, .. } => name,
+        }
+    }
+
+    pub fn elements(&self) -> &[Element] {
+        match self {
+            Track::Video { elements, .. }
+            | Track::Text { elements, .. }
+            | Track::Audio { elements, .. }
+            | Track::Graphic { elements, .. }
+            | Track::Effect { elements, .. } => elements,
+        }
+    }
+
+    pub fn elements_mut(&mut self) -> &mut Vec<Element> {
+        match self {
+            Track::Video { elements, .. }
+            | Track::Text { elements, .. }
+            | Track::Audio { elements, .. }
+            | Track::Graphic { elements, .. }
+            | Track::Effect { elements, .. } => elements,
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
+pub struct SceneTracks {
+    pub overlay: Vec<Track>,
+    pub main: Track,
+    pub audio: Vec<Track>,
+}