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, 97 insertions, 0 deletions

diff --git a/rust/crates/timeline/src/audio_separation.rs b/rust/crates/timeline/src/audio_separation.rs
new file mode 100644
index 00000000..67494380
--- /dev/null
+++ b/rust/crates/timeline/src/audio_separation.rs
@@ -0,0 +1,97 @@
+use scene::{Element, ElementAnimations, ParamValue, ParamValues, UploadAudioElement, VideoElement};
+
+use crate::defaults::DEFAULT_VOLUME;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct MediaAudioState {
+    pub has_audio: Option<bool>,
+}
+
+pub fn is_source_audio_enabled(element: &VideoElement) -> bool {
+    element.is_source_audio_enabled != Some(false)
+}
+
+pub fn is_source_audio_separated(element: &VideoElement) -> bool {
+    !is_source_audio_enabled(element)
+}
+
+pub fn can_extract_source_audio(element: &Element, media_asset: Option<&MediaAudioState>) -> bool {
+    let Element::Video(video) = element else {
+        return false;
+    };
+    is_source_audio_enabled(video) && media_asset.is_some_and(|media| media.has_audio != Some(false))
+}
+
+pub fn can_recover_source_audio(element: &Element) -> bool {
+    let Element::Video(video) = element else {
+        return false;
+    };
+    is_source_audio_separated(video)
+}
+
+pub fn can_toggle_source_audio(element: &Element, media_asset: Option<&MediaAudioState>) -> bool {
+    can_recover_source_audio(element) || can_extract_source_audio(element, media_asset)
+}
+
+pub fn does_element_have_enabled_audio(
+    element: &Element,
+    media_asset: Option<&MediaAudioState>,
+) -> bool {
+    match element {
+        Element::Audio(_) => true,
+        Element::Video(video) => {
+            media_asset.is_some_and(|media| media.has_audio != Some(false))
+                && is_source_audio_enabled(video)
+        }
+        _ => false,
+    }
+}
+
+pub fn build_separated_audio_element(
+    source_element: &VideoElement,
+    id: impl Into<String>,
+) -> UploadAudioElement {
+    let source_base = &source_element.base;
+
+    let mut params = ParamValues::new();
+    let volume = match source_base.params.get("volume") {
+        Some(ParamValue::Number(volume)) => *volume,
+        _ => DEFAULT_VOLUME,
+    };
+    params.insert("volume".to_string(), ParamValue::Number(volume));
+    params.insert(
+        "muted".to_string(),
+        ParamValue::Bool(source_base.params.get("muted") == Some(&ParamValue::Bool(true))),
+    );
+
+    UploadAudioElement {
+        base: scene::BaseTimelineElement {
+            id: id.into(),
+            name: source_base.name.clone(),
+            duration: source_base.duration,
+            start_time: source_base.start_time,
+            trim_start: source_base.trim_start,
+            trim_end: source_base.trim_end,
+            source_duration: source_base.source_duration,
+            animations: clone_volume_animations(source_base.animations.as_ref()),
+            params,
+        },
+        retime: source_element.retime,
+        media_id: source_element.media_id.clone(),
+    }
+}
+
+pub fn get_source_audio_action_label(element: &VideoElement) -> &'static str {
+    if is_source_audio_separated(element) {
+        "Recover audio"
+    } else {
+        "Extract audio"
+    }
+}
+
+fn clone_volume_animations(animations: Option<&ElementAnimations>) -> Option<ElementAnimations> {
+    let volume_data = animations?.get("volume")?;
+    let mut volume_only = ElementAnimations::new();
+    volume_only.insert("volume".to_string(), volume_data.clone());
+    animation::clone_animations(Some(&volume_only), true)
+}