fix: create /dev/nvidia* nodes in bee-nvidia — mdev has no NVIDIA rules

Alpine uses mdev which has no rules for NVIDIA devices. Without /dev/nvidiactl
and /dev/nvidia{0-7}, nvidia-smi returns NVML_ERROR_LIBRARY_NOT_FOUND (exit 12)
even though kernel modules are loaded and libraries are present.

Fix: after insmod, read major numbers from /proc/devices and mknod the required
character devices (/dev/nvidiactl, /dev/nvidia{0-7}, /dev/nvidia-uvm).

Add /dev/nvidia* node checks to smoketest for earlier failure detection.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/overlay/etc/init.d/bee-nvidia

@@ -47,5 +47,26 @@ start() {
         fi
     done
 
+    # Create /dev/nvidia* device nodes — mdev on Alpine does not have NVIDIA rules,
+    # so the kernel hotplug events are not handled and nodes are never created.
+    # Without /dev/nvidiactl nvidia-smi returns NVML_ERROR_LIBRARY_NOT_FOUND (exit 12).
+    nvidia_major=$(grep -m1 ' nvidiactl$' /proc/devices 2>/dev/null | awk '{print $1}')
+    if [ -n "$nvidia_major" ]; then
+        mknod -m 666 /dev/nvidiactl c "$nvidia_major" 255 2>/dev/null || true
+        for i in 0 1 2 3 4 5 6 7; do
+            mknod -m 666 "/dev/nvidia$i" c "$nvidia_major" "$i" 2>/dev/null || true
+        done
+        einfo "created /dev/nvidiactl and /dev/nvidia{0-7} (major $nvidia_major)"
+    else
+        ewarn "/dev/nvidiactl: nvidia not in /proc/devices — no GPU hardware?"
+    fi
+
+    uvm_major=$(grep -m1 ' nvidia-uvm$' /proc/devices 2>/dev/null | awk '{print $1}')
+    if [ -n "$uvm_major" ]; then
+        mknod -m 666 /dev/nvidia-uvm       c "$uvm_major" 0 2>/dev/null || true
+        mknod -m 666 /dev/nvidia-uvm-tools c "$uvm_major" 1 2>/dev/null || true
+        einfo "created /dev/nvidia-uvm (major $uvm_major)"
+    fi
+
     eend 0
 }