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, 190 insertions, 0 deletions

diff --git a/rust/crates/scene/tests/round_trip.rs b/rust/crates/scene/tests/round_trip.rs
new file mode 100644
index 00000000..8e26c1f7
--- /dev/null
+++ b/rust/crates/scene/tests/round_trip.rs
@@ -0,0 +1,190 @@
+#![recursion_limit = "256"]
+
+use ::scene::*;
+
+fn sample_project_json() -> serde_json::Value {
+    serde_json::json!({
+        "metadata": {
+            "id": "proj-1",
+            "name": "Demo",
+            "duration": 10000,
+            "createdAt": "2026-07-28T10:00:00.000Z",
+            "updatedAt": "2026-07-28T11:30:00.000Z"
+        },
+        "scenes": [{
+            "id": "scene-1",
+            "name": "Main scene",
+            "isMain": true,
+            "tracks": {
+                "overlay": [
+                    {
+                        "type": "text",
+                        "id": "track-text",
+                        "name": "Text",
+                        "hidden": false,
+                        "elements": [{
+                            "type": "text",
+                            "id": "el-text",
+                            "name": "Title",
+                            "duration": 2000,
+                            "startTime": 0,
+                            "trimStart": 0,
+                            "trimEnd": 0,
+                            "params": { "content": "Hello", "fontSize": 48, "bold": true },
+                            "animations": {
+                                "opacity": {
+                                    "keys": [
+                                        { "id": "k1", "time": 0, "value": 0, "segmentToNext": "linear", "tangentMode": "auto" },
+                                        { "id": "k2", "time": 500, "value": 1, "leftHandle": { "dt": -100, "dv": -0.1 }, "rightHandle": { "dt": 100, "dv": 0.1 }, "segmentToNext": "bezier", "tangentMode": "aligned" }
+                                    ],
+                                    "extrapolation": { "before": "hold", "after": "linear" }
+                                },
+                                "color": {
+                                    "r": { "keys": [{ "id": "k3", "time": 0, "value": 0.5, "segmentToNext": "step", "tangentMode": "flat" }] },
+                                    "g": { "keys": [{ "id": "k4", "time": 0, "value": 0.2, "segmentToNext": "linear", "tangentMode": "auto" }] }
+                                }
+                            },
+                            "effects": [{ "id": "fx1", "type": "blur", "params": { "radius": 4 }, "enabled": true }]
+                        }]
+                    }
+                ],
+                "main": {
+                    "type": "video",
+                    "id": "track-main",
+                    "name": "Main",
+                    "muted": false,
+                    "hidden": false,
+                    "elements": [
+                        {
+                            "type": "video",
+                            "id": "el-video",
+                            "name": "Clip",
+                            "duration": 5000,
+                            "startTime": 0,
+                            "trimStart": 100,
+                            "trimEnd": 200,
+                            "sourceDuration": 6000,
+                            "mediaId": "media-1",
+                            "isSourceAudioEnabled": true,
+                            "retime": { "rate": 1.5, "maintainPitch": true },
+                            "params": {},
+                            "masks": [
+                                { "id": "m1", "type": "rectangle", "params": { "feather": 2, "inverted": false, "strokeColor": "#fff", "strokeWidth": 1, "strokeAlign": "inside", "centerX": 0, "centerY": 0, "width": 100, "height": 50, "rotation": 0, "scale": 1 } },
+                                { "id": "m2", "type": "freeform", "params": { "feather": 0, "inverted": true, "strokeColor": "#000", "strokeWidth": 0, "strokeAlign": "center", "path": [{ "id": "p1", "x": 0, "y": 0, "inX": -1, "inY": 0, "outX": 1, "outY": 0 }], "closed": true, "centerX": 10, "centerY": 20, "rotation": 15, "scale": 2 } },
+                                { "id": "m3", "type": "cinematic-bars", "params": { "feather": 0, "inverted": false, "strokeColor": "#000", "strokeWidth": 0, "strokeAlign": "outside", "centerX": 0, "centerY": 0, "width": 1920, "height": 200, "rotation": 0, "scale": 1 } }
+                            ]
+                        },
+                        {
+                            "type": "image",
+                            "id": "el-image",
+                            "name": "Still",
+                            "duration": 3000,
+                            "startTime": 5000,
+                            "trimStart": 0,
+                            "trimEnd": 0,
+                            "mediaId": "media-2",
+                            "hidden": false,
+                            "params": {}
+                        }
+                    ]
+                },
+                "audio": [
+                    {
+                        "type": "audio",
+                        "id": "track-audio",
+                        "name": "Audio",
+                        "muted": false,
+                        "elements": [
+                            {
+                                "type": "audio",
+                                "sourceType": "upload",
+                                "id": "el-au1",
+                                "name": "Music",
+                                "duration": 8000,
+                                "startTime": 0,
+                                "trimStart": 0,
+                                "trimEnd": 0,
+                                "mediaId": "media-3",
+                                "retime": { "rate": 1 },
+                                "params": { "volume": 0.8 }
+                            },
+                            {
+                                "type": "audio",
+                                "sourceType": "library",
+                                "id": "el-au2",
+                                "name": "Sfx",
+                                "duration": 1000,
+                                "startTime": 2000,
+                                "trimStart": 0,
+                                "trimEnd": 0,
+                                "sourceUrl": "https://example.com/sfx.mp3",
+                                "params": {}
+                            }
+                        ]
+                    }
+                ]
+            },
+            "bookmarks": [{ "time": 1500, "note": "cut here", "color": "red", "duration": 250 }],
+            "createdAt": "2026-07-28T10:00:00.000Z",
+            "updatedAt": "2026-07-28T11:00:00.000Z"
+        }],
+        "currentSceneId": "scene-1",
+        "settings": {
+            "fps": { "numerator": 30, "denominator": 1 },
+            "canvasSize": { "width": 1920, "height": 1080 },
+            "canvasSizeMode": "preset",
+            "background": { "type": "blur", "blurIntensity": 8 }
+        },
+        "version": 7,
+        "timelineViewState": { "zoomLevel": 2, "scrollLeft": 120, "playheadTime": 750 }
+    })
+}
+
+fn diff_path(a: &serde_json::Value, b: &serde_json::Value, path: &str) {
+    match (a, b) {
+        (serde_json::Value::Object(x), serde_json::Value::Object(y)) => {
+            for key in x.keys().chain(y.keys()) {
+                if x.get(key) != y.get(key) {
+                    diff_path(
+                        x.get(key).unwrap_or(&serde_json::Value::Null),
+                        y.get(key).unwrap_or(&serde_json::Value::Null),
+                        &format!("{path}.{key}"),
+                    );
+                    return;
+                }
+            }
+        }
+        (serde_json::Value::Array(x), serde_json::Value::Array(y)) => {
+            for (i, (u, v)) in x.iter().zip(y.iter()).enumerate() {
+                if u != v {
+                    diff_path(u, v, &format!("{path}[{i}]"));
+                    return;
+                }
+            }
+            if x.len() != y.len() {
+                panic!("length mismatch at {path}: {} vs {}", x.len(), y.len());
+            }
+        }
+        (serde_json::Value::Number(x), serde_json::Value::Number(y))
+            if x.as_f64() == y.as_f64() => {}
+        _ => panic!("mismatch at {path}:\n  serialized: {a}\n  original:   {b}"),
+    }
+}
+
+#[test]
+fn project_round_trip_preserves_json() {
+    let original = sample_project_json();
+    let project: Project = serde_json::from_value(original.clone()).expect("deserialize");
+    let serialized = serde_json::to_value(&project).expect("serialize");
+    diff_path(&serialized, &original, "$");
+}
+
+#[test]
+fn element_accessors_reach_base() {
+    let original = sample_project_json();
+    let project: Project = serde_json::from_value(original).expect("deserialize");
+    let main = &project.scenes[0].tracks.main;
+    let video = &main.elements()[0];
+    assert_eq!(video.base().id, "el-video");
+    assert_eq!(video.base().trim_start, time::MediaTime::from_ticks(100));
+}