The original design used onPointerUp to cycle agents, which doesn't trigger
focus transfer and keeps the soft keyboard open. Recent changes switched to
onClick which causes button to gain focus and closes the keyboard.
- Remove onClick handler entirely
- Restore handlePointerDown, handlePointerUp, handlePointerLeave handlers
- Use onPointerUp to trigger agent cycling
- Add onContextMenu to prevent context menu on long-press
- Add extensive comments explaining why pointer events must be used
This reverts to the behavior from commit 337c458f where clicking the agent
button doesn't close the soft keyboard.
Co-authored-by: Jovines <jovines@qq.com>
