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, 46 insertions, 0 deletions

diff --git a/rust/crates/commands/src/scene/create_scene.rs b/rust/crates/commands/src/scene/create_scene.rs
new file mode 100644
index 00000000..1f2de02b
--- /dev/null
+++ b/rust/crates/commands/src/scene/create_scene.rs
@@ -0,0 +1,46 @@
+use scene::{Project, Scene};
+
+use crate::command::{Command, CommandError, CommandResult};
+
+pub struct CreateSceneCommand {
+    name: String,
+    is_main: bool,
+    saved_scenes: Option<Vec<Scene>>,
+    created_scene_id: Option<String>,
+}
+
+impl CreateSceneCommand {
+    pub fn new(name: impl Into<String>, is_main: bool) -> Self {
+        Self {
+            name: name.into(),
+            is_main,
+            saved_scenes: None,
+            created_scene_id: None,
+        }
+    }
+
+    pub fn scene_id(&self) -> Option<&str> {
+        self.created_scene_id.as_deref()
+    }
+}
+
+impl Command for CreateSceneCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        self.saved_scenes = Some(project.scenes.clone());
+
+        let created = timeline::scenes::build_default_scene(&self.name, self.is_main);
+        self.created_scene_id = Some(created.id.clone());
+        project.scenes.push(created);
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let Some(saved) = &self.saved_scenes else {
+            return;
+        };
+        project.scenes = saved.clone();
+    }
+}