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, 96 insertions, 0 deletions

diff --git a/rust/crates/timeline/src/lib.rs b/rust/crates/timeline/src/lib.rs
new file mode 100644
index 00000000..e724b5bc
--- /dev/null
+++ b/rust/crates/timeline/src/lib.rs
@@ -0,0 +1,96 @@
+use scene::{AudioElement, Element, RetimeConfig, SceneTracks};
+use time::MediaTime;
+
+pub mod audio_separation;
+pub mod creation;
+pub mod defaults;
+pub mod drag_utils;
+pub mod placement;
+pub mod resize;
+pub mod retime;
+pub mod ripple;
+pub mod scenes;
+pub mod snap;
+pub mod split;
+pub mod track_capabilities;
+pub mod track_element_update;
+pub mod types;
+pub mod update_pipeline;
+
+pub use audio_separation::*;
+pub use creation::*;
+pub use track_capabilities::*;
+pub use track_element_update::*;
+pub use types::{ElementType, TrackType};
+
+pub fn calculate_total_duration(tracks: &SceneTracks) -> MediaTime {
+    placement::ordered_tracks(tracks)
+        .iter()
+        .flat_map(|track| track.elements().iter())
+        .map(|element| element.base().start_time + element.base().duration)
+        .fold(MediaTime::ZERO, MediaTime::max)
+}
+
+pub fn is_visual_element(element: &Element) -> bool {
+    matches!(
+        element,
+        Element::Video(_)
+            | Element::Image(_)
+            | Element::Text(_)
+            | Element::Sticker(_)
+            | Element::Graphic(_)
+    )
+}
+
+pub fn is_maskable_element(element: &Element) -> bool {
+    matches!(element, Element::Video(_) | Element::Image(_) | Element::Graphic(_))
+}
+
+pub fn is_retimable_element(element: &Element) -> bool {
+    matches!(element, Element::Video(_) | Element::Audio(_))
+}
+
+pub fn can_element_have_audio(element: &Element) -> bool {
+    matches!(element, Element::Audio(_) | Element::Video(_))
+}
+
+pub fn can_element_be_hidden(element: &Element) -> bool {
+    is_visual_element(element)
+}
+
+pub fn has_element_effects(element: &Element) -> bool {
+    let effects = match element {
+        Element::Video(video) => video.effects.as_ref(),
+        Element::Image(image) => image.effects.as_ref(),
+        Element::Text(text) => text.effects.as_ref(),
+        Element::Sticker(sticker) => sticker.effects.as_ref(),
+        Element::Graphic(graphic) => graphic.effects.as_ref(),
+        _ => None,
+    };
+    effects.is_some_and(|effects| !effects.is_empty())
+}
+
+pub fn has_media_id(element: &Element) -> bool {
+    matches!(
+        element,
+        Element::Audio(AudioElement::Upload(_)) | Element::Video(_) | Element::Image(_)
+    )
+}
+
+pub fn element_retime(element: &Element) -> Option<RetimeConfig> {
+    match element {
+        Element::Video(video) => video.retime,
+        Element::Audio(AudioElement::Upload(audio)) => audio.retime,
+        Element::Audio(AudioElement::Library(audio)) => audio.retime,
+        _ => None,
+    }
+}
+
+pub fn set_element_retime(element: &mut Element, retime: Option<RetimeConfig>) {
+    match element {
+        Element::Video(video) => video.retime = retime,
+        Element::Audio(AudioElement::Upload(audio)) => audio.retime = retime,
+        Element::Audio(AudioElement::Library(audio)) => audio.retime = retime,
+        _ => {}
+    }
+}