fix: use gpus:all for GPU passthrough, detect Docker Desktop in start.sh

docker-compose.override.yml

@@ -1,4 +1,3 @@
 services:
   backend:
-    devices:
-      - nvidia.com/gpu=all
+    gpus: all

docs/design.md

@@ -405,8 +405,10 @@ would wipe the class and leave only the drawings.
 - `docker-compose.yml` — a `backend` service (GPU passthrough, `./data` volume, video archive
   mounted read-write (REQ-178), `.env` for `HF_TOKEN`) and a `frontend` service (nginx: static
   files + `/api` proxy, `client_max_body_size 20g`).
-- GPU access uses **CDI** (`devices: nvidia.com/gpu=all`), not the legacy `runtime: nvidia`.
-  Docker Engine 27+ discovers `nvidia.com/gpu` through the container toolkit; the runtime
-  entry in `/etc/docker/daemon.json` is not registered with the daemon here.
+- GPU access uses compose **`gpus: all`** (same path as the `docker run --gpus all` CLI flag).
+  The earlier CDI form (`devices: nvidia.com/gpu=all`) fails on Docker Desktop's WSL2 backend
+  with `unresolvable CDI devices` because no CDI spec exists there; `gpus: all` works on both
+  Docker Desktop and a native engine with the NVIDIA container toolkit.
+  The runtime entry in `/etc/docker/daemon.json` is not registered with the daemon here.
 - The frontend pins **Vite 7**. Vite 8's default bundler (Rolldown) ships a native binding
   that dies with a bus error on this machine; Vite 7's Rollup path works.

start.sh

@@ -10,8 +10,11 @@ rm -f docker-compose.override.yml
 if command -v nvidia-smi &> /dev/null; then
     echo "✅ NVIDIA GPU detected."
     
-    # 2. Check if the NVIDIA Container Toolkit is installed
+    # 2. Docker Desktop ships its own GPU support; a native engine needs the NVIDIA Container Toolkit
     if ! command -v nvidia-ctk &> /dev/null; then
+        if docker info --format '{{.Name}}' 2>/dev/null | grep -q docker-desktop; then
+            echo "🐳 Docker Desktop detected — GPU support is built in, no toolkit needed."
+        else
             echo "⚠️ NVIDIA Container Toolkit is missing."
             echo "   Without it, Docker cannot access your GPU, and the app will run in CPU-only mode."
             read -p "Would you like to install it automatically now? (requires sudo) [y/N] " install_choice
@@ -30,22 +33,14 @@ if command -v nvidia-smi &> /dev/null; then
                 echo "⚠️ Skipping installation. Proceeding without GPU support."
             fi
         fi
-
-    # 3. If Toolkit is available, configure CDI and enable GPU passthrough
-    if command -v nvidia-ctk &> /dev/null; then
-        if [ ! -f "/etc/cdi/nvidia.yaml" ]; then
-            echo "⚙️ Generating Docker CDI configuration..."
-            sudo nvidia-ctk cdi generate --output=/etc/cdi/nvidia.yaml
     fi
 
     echo "🔌 Enabling GPU support via docker-compose.override.yml..."
     cat <<EOF > docker-compose.override.yml
 services:
   backend:
-    devices:
-      - nvidia.com/gpu=all
+    gpus: all
 EOF
-    fi
 else
     echo "ℹ️ No NVIDIA GPU detected. Running in CPU-only mode."
 fi