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_x11.go

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+//go:build ((linux && !android) || freebsd || openbsd) && !nox11 && !noopengl
+// +build linux,!android freebsd openbsd
+// +build !nox11
+// +build !noopengl
+
+package app
+
+import (
+	"unsafe"
+
+	"gioui.org/internal/egl"
+)
+
+type x11Context struct {
+	win *x11Window
+	*egl.Context
+}
+
+func init() {
+	newX11EGLContext = func(w *x11Window) (context, error) {
+		disp := egl.NativeDisplayType(unsafe.Pointer(w.display()))
+		ctx, err := egl.NewContext(disp)
+		if err != nil {
+			return nil, err
+		}
+		win, _, _ := w.window()
+		eglSurf := egl.NativeWindowType(uintptr(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 &x11Context{win: w, Context: ctx}, nil
+	}
+}
+
+func (c *x11Context) Release() {
+	if c.Context != nil {
+		c.Context.Release()
+		c.Context = nil
+	}
+}
+
+func (c *x11Context) Refresh() error {
+	return nil
+}
+
+func (c *x11Context) Lock() error {
+	return c.Context.MakeCurrent()
+}
+
+func (c *x11Context) Unlock() {
+	c.Context.ReleaseCurrent()
+}