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, 42 insertions, 0 deletions

diff --git a/rust/crates/commands/src/tracks.rs b/rust/crates/commands/src/tracks.rs
new file mode 100644
index 00000000..332a5e6b
--- /dev/null
+++ b/rust/crates/commands/src/tracks.rs
@@ -0,0 +1,42 @@
+use scene::{SceneTracks, Track};
+
+pub fn find_track<'a>(tracks: &'a SceneTracks, track_id: &str) -> Option<&'a Track> {
+    if tracks.main.id() == track_id {
+        return Some(&tracks.main);
+    }
+    tracks
+        .overlay
+        .iter()
+        .find(|track| track.id() == track_id)
+        .or_else(|| tracks.audio.iter().find(|track| track.id() == track_id))
+}
+
+pub fn find_track_mut<'a>(
+    tracks: &'a mut SceneTracks,
+    track_id: &str,
+) -> Option<&'a mut Track> {
+    if tracks.main.id() == track_id {
+        return Some(&mut tracks.main);
+    }
+    tracks
+        .overlay
+        .iter_mut()
+        .find(|track| track.id() == track_id)
+        .or_else(|| tracks.audio.iter_mut().find(|track| track.id() == track_id))
+}
+
+pub fn all_tracks(tracks: &SceneTracks) -> impl Iterator<Item = &Track> {
+    tracks
+        .overlay
+        .iter()
+        .chain(std::iter::once(&tracks.main))
+        .chain(tracks.audio.iter())
+}
+
+pub fn all_tracks_mut(tracks: &mut SceneTracks) -> impl Iterator<Item = &mut Track> {
+    tracks
+        .overlay
+        .iter_mut()
+        .chain(std::iter::once(&mut tracks.main))
+        .chain(tracks.audio.iter_mut())
+}