steps to reproduce

1. load the zul
2. focus on the 1st textbox
3. press tab 1 time
4. check document.activeElement in the console

current result

1. focus on <span class="z-radio" tabindex="2"></span>
2. when pressing left/right arrow key, we can't move selected radio
3. chrome, firefox, and edge have the same behavior.

expected result

1. focus on <input type="radio">
2. users can move selected radio by arrow keys

debug info

1. Due to <radio> also renders tabindex on both <span> and <input>, so it requires pressing 1 more tab. If I remove the tabindex on the <span>, it works as expected.

   <span id="vYHW4" class="z-radio" tabindex="2"><input type="radio" id="vYHW4-real" name="_pg79o4dn" tabindex="2" checked="checked"><label for="vYHW4-real" id="vYHW4-cnt" class="z-radio-content">yes</label></span>