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/gl_js.go

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package app
+
+import (
+	"errors"
+	"syscall/js"
+
+	"gioui.org/gpu"
+	"gioui.org/internal/gl"
+)
+
+type glContext struct {
+	ctx js.Value
+	cnv js.Value
+	w   *window
+}
+
+func newContext(w *window) (*glContext, error) {
+	args := map[string]interface{}{
+		// Enable low latency rendering.
+		// See https://developers.google.com/web/updates/2019/05/desynchronized.
+		"desynchronized":        true,
+		"preserveDrawingBuffer": true,
+	}
+	ctx := w.cnv.Call("getContext", "webgl2", args)
+	if ctx.IsNull() {
+		ctx = w.cnv.Call("getContext", "webgl", args)
+	}
+	if ctx.IsNull() {
+		return nil, errors.New("app: webgl is not supported")
+	}
+	c := &glContext{
+		ctx: ctx,
+		cnv: w.cnv,
+		w:   w,
+	}
+	return c, nil
+}
+
+func (c *glContext) RenderTarget() (gpu.RenderTarget, error) {
+	if c.w.contextStatus != contextStatusOkay {
+		return nil, gpu.ErrDeviceLost
+	}
+	return gpu.OpenGLRenderTarget{}, nil
+}
+
+func (c *glContext) API() gpu.API {
+	return gpu.OpenGL{Context: gl.Context(c.ctx)}
+}
+
+func (c *glContext) Release() {
+}
+
+func (c *glContext) Present() error {
+	return nil
+}
+
+func (c *glContext) Lock() error {
+	return nil
+}
+
+func (c *glContext) Unlock() {}
+
+func (c *glContext) Refresh() error {
+	switch c.w.contextStatus {
+	case contextStatusLost:
+		return errOutOfDate
+	case contextStatusRestored:
+		c.w.contextStatus = contextStatusOkay
+		return gpu.ErrDeviceLost
+	default:
+		return nil
+	}
+}
+
+func (w *window) NewContext() (context, error) {
+	return newContext(w)
+}