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/io/event/event.go

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// Package event contains types for event handling.
+package event
+
+import (
+	"gioui.org/internal/ops"
+	"gioui.org/op"
+)
+
+// Tag is the stable identifier for an event handler.
+// For a handler h, the tag is typically &h.
+type Tag any
+
+// Event is the marker interface for events.
+type Event interface {
+	ImplementsEvent()
+}
+
+// Filter represents a filter for [Event] types.
+type Filter interface {
+	ImplementsFilter()
+}
+
+// Op declares a tag for input routing at the current transformation
+// and clip area hierarchy. It panics if tag is nil.
+func Op(o *op.Ops, tag Tag) {
+	if tag == nil {
+		panic("Tag must be non-nil")
+	}
+	data := ops.Write1(&o.Internal, ops.TypeInputLen, tag)
+	data[0] = byte(ops.TypeInput)
+}