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/log_windows.go

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package app
+
+import (
+	"log"
+	"unsafe"
+
+	syscall "golang.org/x/sys/windows"
+)
+
+type logger struct{}
+
+var (
+	kernel32           = syscall.NewLazySystemDLL("kernel32")
+	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
+	debugView          *logger
+)
+
+func init() {
+	// Windows DebugView already includes timestamps.
+	if syscall.Stderr == 0 {
+		log.SetFlags(log.Flags() &^ log.LstdFlags)
+		log.SetOutput(debugView)
+	}
+}
+
+func (l *logger) Write(buf []byte) (int, error) {
+	p, err := syscall.UTF16PtrFromString(string(buf))
+	if err != nil {
+		return 0, err
+	}
+	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
+	return len(buf), nil
+}