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

5 files changed, 224 insertions, 0 deletions

diff --git a/rust/crates/commands/src/timeline/track/add_track.rs b/rust/crates/commands/src/timeline/track/add_track.rs
new file mode 100644
index 00000000..d6e9bbae
--- /dev/null
+++ b/rust/crates/commands/src/timeline/track/add_track.rs
@@ -0,0 +1,69 @@
+use scene::{Project, SceneTracks};
+use timeline::placement::{build_empty_track, get_default_insert_index_for_track};
+use timeline::TrackType;
+use uuid::Uuid;
+
+use crate::command::{Command, CommandError, CommandResult};
+use crate::project_ext::active_scene_mut;
+
+pub struct AddTrackCommand {
+    track_type: TrackType,
+    index: Option<usize>,
+    track_id: String,
+    saved_state: Option<SceneTracks>,
+}
+
+impl AddTrackCommand {
+    pub fn new(track_type: TrackType, index: Option<usize>) -> Self {
+        Self {
+            track_type,
+            index,
+            track_id: Uuid::new_v4().to_string(),
+            saved_state: None,
+        }
+    }
+
+    pub fn track_id(&self) -> &str {
+        &self.track_id
+    }
+}
+
+impl Command for AddTrackCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        let Some(scene) = active_scene_mut(project) else {
+            return Ok(None);
+        };
+
+        self.saved_state = Some(scene.tracks.clone());
+
+        let insert_index = self.index.unwrap_or_else(|| {
+            get_default_insert_index_for_track(&scene.tracks, self.track_type)
+        });
+
+        let new_track = build_empty_track(&self.track_id, self.track_type, None);
+        if self.track_type == TrackType::Audio {
+            let audio_insert_index = insert_index
+                .saturating_sub(scene.tracks.overlay.len() + 1);
+            scene
+                .tracks
+                .audio
+                .insert(audio_insert_index.min(scene.tracks.audio.len()), new_track);
+        } else {
+            let overlay_insert_index = insert_index.min(scene.tracks.overlay.len());
+            scene.tracks.overlay.insert(overlay_insert_index, new_track);
+        }
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let Some(saved) = &self.saved_state else {
+            return;
+        };
+        if let Some(scene) = active_scene_mut(project) {
+            scene.tracks = saved.clone();
+        }
+    }
+}
diff --git a/rust/crates/commands/src/timeline/track/mod.rs b/rust/crates/commands/src/timeline/track/mod.rs
new file mode 100644
index 00000000..c133a12d
--- /dev/null
+++ b/rust/crates/commands/src/timeline/track/mod.rs
@@ -0,0 +1,9 @@
+pub mod add_track;
+pub mod remove_track;
+pub mod toggle_track_mute;
+pub mod toggle_track_visibility;
+
+pub use add_track::AddTrackCommand;
+pub use remove_track::RemoveTrackCommand;
+pub use toggle_track_mute::ToggleTrackMuteCommand;
+pub use toggle_track_visibility::ToggleTrackVisibilityCommand;
diff --git a/rust/crates/commands/src/timeline/track/remove_track.rs b/rust/crates/commands/src/timeline/track/remove_track.rs
new file mode 100644
index 00000000..5a79b4ae
--- /dev/null
+++ b/rust/crates/commands/src/timeline/track/remove_track.rs
@@ -0,0 +1,43 @@
+use scene::{Project, SceneTracks};
+
+use crate::command::{Command, CommandError, CommandResult};
+use crate::project_ext::active_scene_mut;
+
+pub struct RemoveTrackCommand {
+    track_id: String,
+    saved_state: Option<SceneTracks>,
+}
+
+impl RemoveTrackCommand {
+    pub fn new(track_id: impl Into<String>) -> Self {
+        Self {
+            track_id: track_id.into(),
+            saved_state: None,
+        }
+    }
+}
+
+impl Command for RemoveTrackCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        let Some(scene) = active_scene_mut(project) else {
+            return Ok(None);
+        };
+
+        self.saved_state = Some(scene.tracks.clone());
+        scene.tracks.overlay.retain(|track| track.id() != self.track_id);
+        scene.tracks.audio.retain(|track| track.id() != self.track_id);
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let Some(saved) = &self.saved_state else {
+            return;
+        };
+        if let Some(scene) = active_scene_mut(project) {
+            scene.tracks = saved.clone();
+        }
+    }
+}
diff --git a/rust/crates/commands/src/timeline/track/toggle_track_mute.rs b/rust/crates/commands/src/timeline/track/toggle_track_mute.rs
new file mode 100644
index 00000000..afaaf3f3
--- /dev/null
+++ b/rust/crates/commands/src/timeline/track/toggle_track_mute.rs
@@ -0,0 +1,49 @@
+use scene::{Project, SceneTracks, Track};
+
+use crate::command::{Command, CommandError, CommandResult};
+use crate::project_ext::active_scene_mut;
+use crate::tracks::find_track_mut;
+
+pub struct ToggleTrackMuteCommand {
+    track_id: String,
+    saved_state: Option<SceneTracks>,
+}
+
+impl ToggleTrackMuteCommand {
+    pub fn new(track_id: impl Into<String>) -> Self {
+        Self {
+            track_id: track_id.into(),
+            saved_state: None,
+        }
+    }
+}
+
+impl Command for ToggleTrackMuteCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        let Some(scene) = active_scene_mut(project) else {
+            return Ok(None);
+        };
+
+        self.saved_state = Some(scene.tracks.clone());
+
+        match find_track_mut(&mut scene.tracks, &self.track_id) {
+            Some(Track::Video { muted, .. }) | Some(Track::Audio { muted, .. }) => {
+                *muted = !*muted;
+            }
+            _ => {}
+        }
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let Some(saved) = &self.saved_state else {
+            return;
+        };
+        if let Some(scene) = active_scene_mut(project) {
+            scene.tracks = saved.clone();
+        }
+    }
+}
diff --git a/rust/crates/commands/src/timeline/track/toggle_track_visibility.rs b/rust/crates/commands/src/timeline/track/toggle_track_visibility.rs
new file mode 100644
index 00000000..79000a73
--- /dev/null
+++ b/rust/crates/commands/src/timeline/track/toggle_track_visibility.rs
@@ -0,0 +1,54 @@
+use scene::{Project, SceneTracks, Track};
+
+use crate::command::{Command, CommandError, CommandResult};
+use crate::project_ext::active_scene_mut;
+use crate::tracks::find_track_mut;
+
+pub struct ToggleTrackVisibilityCommand {
+    track_id: String,
+    saved_state: Option<SceneTracks>,
+}
+
+impl ToggleTrackVisibilityCommand {
+    pub fn new(track_id: impl Into<String>) -> Self {
+        Self {
+            track_id: track_id.into(),
+            saved_state: None,
+        }
+    }
+}
+
+impl Command for ToggleTrackVisibilityCommand {
+    fn execute(
+        &mut self,
+        project: &mut Project,
+    ) -> Result<Option<CommandResult>, CommandError> {
+        let Some(scene) = active_scene_mut(project) else {
+            return Ok(None);
+        };
+
+        self.saved_state = Some(scene.tracks.clone());
+
+        match find_track_mut(&mut scene.tracks, &self.track_id) {
+            Some(
+                Track::Video { hidden, .. }
+                | Track::Text { hidden, .. }
+                | Track::Graphic { hidden, .. }
+                | Track::Effect { hidden, .. },
+            ) => {
+                *hidden = !*hidden;
+            }
+            _ => {}
+        }
+        Ok(None)
+    }
+
+    fn undo(&mut self, project: &mut Project) {
+        let Some(saved) = &self.saved_state else {
+            return;
+        };
+        if let Some(scene) = active_scene_mut(project) {
+            scene.tracks = saved.clone();
+        }
+    }
+}