solid: verticalScrollbarOptions.onChange is not wired through the prop

Summary

Passing verticalScrollbarOptions={{ onChange }} to <scrollbox> never invokes the callback.

Environment

• @opentui/core 0.5.11, @opentui/solid 0.5.11
• Bun 1.4.0, Linux

Steps to reproduce

1. Render <scrollbox verticalScrollbarOptions={{ onChange: (position) => ... }}>.
2. Scroll the box (wheel/keys).

Actual

The callback never fires. The Solid prop setter assigns the options object after construction, and the internal _onChange sink used by the scrollbar construction path never gets set.

Expected

The callback should be wired when passed through verticalScrollbarOptions, or a dedicated onScroll/onChange prop should exist on the scrollbox.

Workaround

Subscribe to the public event instead: scrollbox.verticalScrollBar.on("change", (position) => ...).