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/app/egl_windows.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+//go:build !noopengl
+
+package app
+
+import (
+	"gioui.org/internal/egl"
+)
+
+type glContext struct {
+	win *window
+	*egl.Context
+}
+
+func init() {
+	drivers = append(drivers, gpuAPI{
+		priority: 2,
+		initializer: func(w *window) (context, error) {
+			disp := egl.NativeDisplayType(w.HDC())
+			ctx, err := egl.NewContext(disp)
+			if err != nil {
+				return nil, err
+			}
+			win, _, _ := w.HWND()
+			eglSurf := egl.NativeWindowType(win)
+			if err := ctx.CreateSurface(eglSurf); err != nil {
+				ctx.Release()
+				return nil, err
+			}
+			if err := ctx.MakeCurrent(); err != nil {
+				ctx.Release()
+				return nil, err
+			}
+			defer ctx.ReleaseCurrent()
+			ctx.EnableVSync(true)
+			return &glContext{win: w, Context: ctx}, nil
+		},
+	})
+}
+
+func (c *glContext) Release() {
+	if c.Context != nil {
+		c.Context.Release()
+		c.Context = nil
+	}
+}
+
+func (c *glContext) Refresh() error {
+	return nil
+}
+
+func (c *glContext) Lock() error {
+	return c.Context.MakeCurrent()
+}
+
+func (c *glContext) Unlock() {
+	c.Context.ReleaseCurrent()
+}