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, 14 insertions, 0 deletions

diff --git a/rust/crates/timeline/src/drag_utils.rs b/rust/crates/timeline/src/drag_utils.rs
new file mode 100644
index 00000000..6dcc6c6f
--- /dev/null
+++ b/rust/crates/timeline/src/drag_utils.rs
@@ -0,0 +1,14 @@
+use time::{MediaTime, TICKS_PER_SECOND};
+
+use crate::snap::BASE_TIMELINE_PIXELS_PER_SECOND;
+
+pub fn get_mouse_time_from_client_x(
+    client_x: f64,
+    container_left: f64,
+    zoom_level: f64,
+    scroll_left: f64,
+) -> MediaTime {
+    let mouse_x = client_x - container_left + scroll_left;
+    let seconds = (mouse_x / (BASE_TIMELINE_PIXELS_PER_SECOND * zoom_level)).max(0.0);
+    MediaTime::from_ticks((seconds * TICKS_PER_SECOND as f64).round() as i64)
+}