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/layout/context.go

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package layout
+
+import (
+	"time"
+
+	"gioui.org/io/input"
+	"gioui.org/io/system"
+	"gioui.org/op"
+	"gioui.org/unit"
+)
+
+// Context carries the state needed by almost all layouts and widgets.
+// A zero value Context never returns events, map units to pixels
+// with a scale of 1.0, and returns the zero time from Now.
+type Context struct {
+	// Constraints track the constraints for the active widget or
+	// layout.
+	Constraints Constraints
+
+	Metric unit.Metric
+	// Now is the animation time.
+	Now time.Time
+
+	// Locale provides information on the system's language preferences.
+	// BUG(whereswaldon): this field is not currently populated automatically.
+	// Interested users must look up and populate these values manually.
+	Locale system.Locale
+
+	// Values is a map of program global data associated with the context.
+	// It is not for use by widgets.
+	Values map[string]any
+
+	input.Source
+	*op.Ops
+}
+
+// Dp converts v to pixels.
+func (c Context) Dp(v unit.Dp) int {
+	return c.Metric.Dp(v)
+}
+
+// Sp converts v to pixels.
+func (c Context) Sp(v unit.Sp) int {
+	return c.Metric.Sp(v)
+}
+
+// Disabled returns a copy of this context that don't deliver any events.
+func (c Context) Disabled() Context {
+	c.Source = c.Source.Disabled()
+	return c
+}