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/shader.go

@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package shader
+
+type Sources struct {
+	Name           string
+	SPIRV          string
+	GLSL100ES      string
+	GLSL150        string
+	DXBC           string
+	MetalLib       string
+	Uniforms       UniformsReflection
+	Inputs         []InputLocation
+	Textures       []TextureBinding
+	StorageBuffers []BufferBinding
+	Images         []ImageBinding
+	WorkgroupSize  [3]int
+}
+
+type UniformsReflection struct {
+	Locations []UniformLocation
+	Size      int
+}
+
+type ImageBinding struct {
+	Name    string
+	Binding int
+}
+
+type BufferBinding struct {
+	Name    string
+	Binding int
+}
+
+type TextureBinding struct {
+	Name    string
+	Binding int
+}
+
+type UniformLocation struct {
+	Name   string
+	Type   DataType
+	Size   int
+	Offset int
+}
+
+type InputLocation struct {
+	// For GLSL.
+	Name     string
+	Location int
+	// For HLSL.
+	Semantic      string
+	SemanticIndex int
+
+	Type DataType
+	Size int
+}
+
+type DataType uint8
+
+const (
+	DataTypeFloat DataType = iota
+	DataTypeInt
+	DataTypeShort
+)