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/widget/material/doc.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// Package material implements the Material design.
+//
+// To maximize reusability and visual flexibility, user interface controls are
+// split into two parts: the stateful widget and the stateless drawing of it.
+//
+// For example, widget.Clickable encapsulates the state and event
+// handling of all clickable areas, while the Theme is responsible to
+// draw a specific area, for example a button.
+//
+// This snippet defines a button that prints a message when clicked:
+//
+//	var gtx layout.Context
+//	button := new(widget.Clickable)
+//
+//	for button.Clicked(gtx) {
+//	    fmt.Println("Clicked!")
+//	}
+//
+// Use a Theme to draw the button:
+//
+//	theme := material.NewTheme(...)
+//
+//	material.Button(theme, button, "Click me!").Layout(gtx)
+//
+// # Customization
+//
+// Quite often, a program needs to customize the theme-provided defaults. Several
+// options are available, depending on the nature of the change.
+//
+// Mandatory parameters: Some parameters are not part of the widget state but
+// have no obvious default. In the program above, the button text is a
+// parameter to the Theme.Button method.
+//
+// Theme-global parameters: For changing the look of all widgets drawn with a
+// particular theme, adjust the `Theme` fields:
+//
+//	theme.Palette.Fg = color.NRGBA{...}
+//
+// Widget-local parameters: For changing the look of a particular widget,
+// adjust the widget specific theme object:
+//
+//	btn := material.Button(theme, button, "Click me!")
+//	btn.Font.Style = text.Italic
+//	btn.Layout(gtx)
+//
+// Widget variants: A widget can have several distinct representations even
+// though the underlying state is the same. A widget.Clickable can be drawn as a
+// round icon button:
+//
+//	icon := widget.NewIcon(...)
+//
+//	material.IconButton(theme, button, icon, "Click me!").Layout(gtx)
+//
+// Specialized widgets: Theme both define a generic Label method
+// that takes a text size, and specialized methods for standard text
+// sizes such as Theme.H1 and Theme.Body2.
+package material