Fix sortable column hover area

[ganyicz]

The scenario

Hovering over sortable column only affects the nested button, not the full header cell.

But clicking works on the entire cell.

Screen.Recording.2026-02-06.at.20.48.11.mov

The problem

The wire:click is added to the th, but the hover group is on the <button>:

<th {{ $attributes->class($classes) }}> {{-- wire:click --}}
    <button class="group/sortable ..."> {{-- hover area --}}
        <div class="group-hover/sortable:opacity-100"> ... </div>
    </button>
</th>

The solution

Move group/sortable from the <button> to the <th>.

<th class="... group/sortable">
    <button class="flex items-center ...">
</th>

Screen.Recording.2026-02-06.at.20.53.09.mov

Fixes #2362