chore(v2): vendor dependencies for offline/China builds

go mod vendor pins onnxruntime_go v1.12.1, Gio and the rest into v2/vendor
so go run/build work without hitting proxy.golang.org (blocked/slow in
China). Verified: CGO_ENABLED=1 go build -mod=vendor ./internal/spike and
GOOS=windows go build -mod=vendor ./internal/ui both pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v2/vendor/gioui.org/shader/gio/zmaterial.frag.0.glsl150

@@ -0,0 +1,36 @@
+#version 150
+
+struct Color
+{
+    float emulateSRGB;
+};
+
+uniform Color _color;
+
+uniform sampler2D tex;
+
+in vec2 vUV;
+out vec4 fragColor;
+
+vec3 RGBtosRGB(vec3 rgb)
+{
+    bvec3 cutoff = greaterThanEqual(rgb, vec3(0.003130800090730190277099609375));
+    vec3 below = vec3(12.9200000762939453125) * rgb;
+    vec3 above = (vec3(1.05499994754791259765625) * pow(rgb, vec3(0.416660010814666748046875))) - vec3(0.054999999701976776123046875);
+    return vec3(cutoff.x ? above.x : below.x, cutoff.y ? above.y : below.y, cutoff.z ? above.z : below.z);
+}
+
+void main()
+{
+    vec4 texel = texture(tex, vUV);
+    if (_color.emulateSRGB == 0.0)
+    {
+        vec3 param = texel.xyz;
+        vec3 _71 = RGBtosRGB(param);
+        texel.x = _71.x;
+        texel.y = _71.y;
+        texel.z = _71.z;
+    }
+    fragColor = texel;
+}
+