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/text/text.go

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package text
+
+import (
+	"fmt"
+
+	"gioui.org/io/system"
+	"golang.org/x/image/math/fixed"
+)
+
+type Alignment uint8
+
+const (
+	Start Alignment = iota
+	End
+	Middle
+)
+
+func (a Alignment) String() string {
+	switch a {
+	case Start:
+		return "Start"
+	case End:
+		return "End"
+	case Middle:
+		return "Middle"
+	default:
+		panic("invalid Alignment")
+	}
+}
+
+// Align returns the x offset that should be applied to text with width so that it
+// appears correctly aligned within a space of size maxWidth and with the primary
+// text direction dir.
+func (a Alignment) Align(dir system.TextDirection, width fixed.Int26_6, maxWidth int) fixed.Int26_6 {
+	mw := fixed.I(maxWidth)
+	if dir.Progression() == system.TowardOrigin {
+		switch a {
+		case Start:
+			a = End
+		case End:
+			a = Start
+		}
+	}
+	switch a {
+	case Middle:
+		return (mw - width) / 2
+	case End:
+		return (mw - width)
+	case Start:
+		return 0
+	default:
+		panic(fmt.Errorf("unknown alignment %v", a))
+	}
+}