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/gpu/pack.go

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package gpu
+
+import (
+	"image"
+)
+
+// packer packs a set of many smaller rectangles into
+// much fewer larger atlases.
+type packer struct {
+	maxDims image.Point
+	spaces  []image.Rectangle
+
+	sizes []image.Point
+	pos   image.Point
+}
+
+type placement struct {
+	Idx int
+	Pos image.Point
+}
+
+// add adds the given rectangle to the atlases and
+// return the allocated position.
+func (p *packer) add(s image.Point) (placement, bool) {
+	if place, ok := p.tryAdd(s); ok {
+		return place, true
+	}
+	p.newPage()
+	return p.tryAdd(s)
+}
+
+func (p *packer) clear() {
+	p.sizes = p.sizes[:0]
+	p.spaces = p.spaces[:0]
+}
+
+func (p *packer) newPage() {
+	p.pos = image.Point{}
+	p.sizes = append(p.sizes, image.Point{})
+	p.spaces = p.spaces[:0]
+	p.spaces = append(p.spaces, image.Rectangle{
+		Max: image.Point{X: 1e6, Y: 1e6},
+	})
+}
+
+func (p *packer) tryAdd(s image.Point) (placement, bool) {
+	if len(p.spaces) == 0 || len(p.sizes) == 0 {
+		return placement{}, false
+	}
+
+	var (
+		bestIdx  *image.Rectangle
+		bestSize = p.maxDims
+		lastSize = p.sizes[len(p.sizes)-1]
+	)
+	// Go backwards to prioritize smaller spaces.
+	for i := range p.spaces {
+		space := &p.spaces[i]
+		rightSpace := space.Dx() - s.X
+		bottomSpace := space.Dy() - s.Y
+		if rightSpace < 0 || bottomSpace < 0 {
+			continue
+		}
+		size := lastSize
+		if x := space.Min.X + s.X; x > size.X {
+			if x > p.maxDims.X {
+				continue
+			}
+			size.X = x
+		}
+		if y := space.Min.Y + s.Y; y > size.Y {
+			if y > p.maxDims.Y {
+				continue
+			}
+			size.Y = y
+		}
+		if size.X*size.Y < bestSize.X*bestSize.Y {
+			bestIdx = space
+			bestSize = size
+		}
+	}
+	if bestIdx == nil {
+		return placement{}, false
+	}
+	// Remove space.
+	bestSpace := *bestIdx
+	*bestIdx = p.spaces[len(p.spaces)-1]
+	p.spaces = p.spaces[:len(p.spaces)-1]
+	// Put s in the top left corner and add the (at most)
+	// two smaller spaces.
+	pos := bestSpace.Min
+	if rem := bestSpace.Dy() - s.Y; rem > 0 {
+		p.spaces = append(p.spaces, image.Rectangle{
+			Min: image.Point{X: pos.X, Y: pos.Y + s.Y},
+			Max: image.Point{X: bestSpace.Max.X, Y: bestSpace.Max.Y},
+		})
+	}
+	if rem := bestSpace.Dx() - s.X; rem > 0 {
+		p.spaces = append(p.spaces, image.Rectangle{
+			Min: image.Point{X: pos.X + s.X, Y: pos.Y},
+			Max: image.Point{X: bestSpace.Max.X, Y: pos.Y + s.Y},
+		})
+	}
+	idx := len(p.sizes) - 1
+	p.sizes[idx] = bestSize
+	return placement{Idx: idx, Pos: pos}, true
+}