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, 61 insertions, 0 deletions

diff --git a/rust/crates/commands/src/scene/delete_scene.rs b/rust/crates/commands/src/scene/delete_scene.rs
new file mode 100644
index 00000000..61763dfd
--- /dev/null
+++ b/rust/crates/commands/src/scene/delete_scene.rs
@@ -0,0 +1,61 @@
+use scene::{Project, Scene};
+
+use crate::command::{Command, CommandError, CommandResult};
+
+pub struct DeleteSceneCommand {
+    scene_id: String,
+    saved_scenes: Option<Vec<Scene>>,
+    saved_current_scene_id: Option<String>,
+}
+
+impl DeleteSceneCommand {
+    pub fn new(scene_id: impl Into<String>) -> Self {
+        Self {
+            scene_id: scene_id.into(),
+            saved_scenes: None,
+            saved_current_scene_id: None,
+        }
+    }
+}
+
+impl Command for DeleteSceneCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        let Some(deleted) = project.scenes.iter().find(|scene| scene.id == self.scene_id)
+        else {
+            return Ok(None);
+        };
+        if deleted.is_main {
+            return Ok(None);
+        }
+
+        self.saved_scenes = Some(project.scenes.clone());
+        self.saved_current_scene_id = Some(project.current_scene_id.clone());
+
+        project.scenes.retain(|scene| scene.id != self.scene_id);
+
+        if project.current_scene_id == self.scene_id {
+            let fallback_id = project
+                .scenes
+                .iter()
+                .find(|scene| scene.is_main)
+                .map(|scene| scene.id.clone());
+            if let Some(fallback_id) = fallback_id {
+                project.current_scene_id = fallback_id;
+            }
+        }
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let (Some(saved_scenes), Some(saved_current_scene_id)) =
+            (&self.saved_scenes, &self.saved_current_scene_id)
+        else {
+            return;
+        };
+        project.scenes = saved_scenes.clone();
+        project.current_scene_id = saved_current_scene_id.clone();
+    }
+}