Fix button group styling when buttons are wrapped in tooltips

[joshhanley]

The Scenario

When a button with a tooltip is placed inside a <flux:button.group> (typically via a <flux:modal.trigger>), the button visually breaks out of the group — the border radius isn't welded together and the borders don't collapse properly, making it appear as a separate disconnected button.

This happens with both the tooltip prop on the button and the <flux:tooltip> component wrapper.

<flux:button.group>
    <flux:modal.trigger name="modal-left">
        <flux:button icon="bars-3-bottom-left" tooltip="Left align" />
    </flux:modal.trigger>
    <flux:modal.trigger name="modal-center">
        <flux:button icon="bars-3" tooltip="Center align" />
    </flux:modal.trigger>
    <flux:modal.trigger name="modal-right">
        <flux:button icon="bars-3-bottom-right" tooltip="Right align" />
    </flux:modal.trigger>
</flux:button.group>

The Problem

The button group component uses CSS child selectors to weld buttons together by overriding border-radius and collapsing borders. It handles three nesting depths:

1. Direct children: [&>[data-flux-group-target]:first-child...] — buttons directly in the group
2. One level nested: [&>*:first-child>[data-flux-group-target]...] — button inside one wrapper (e.g., a <flux:modal.trigger> with display: contents)
3. Two levels nested via input: [&>*:first-child>[data-flux-input]>[data-flux-group-target]...] — button inside two wrappers (e.g., combobox)

When a tooltip wraps a button inside a <flux:modal.trigger>, the DOM structure becomes:

button-group > div.contents (modal trigger) > ui-tooltip > button

The <flux:modal.trigger> uses display: contents so it's invisible to layout, but CSS selectors still see it in the DOM tree. The one-level selectors don't match because the button isn't a direct child of the modal trigger — the <ui-tooltip> element sits between them. And the two-level selectors only target [data-flux-input] as the intermediate element, not [data-flux-tooltip].

The Solution

Added targeted [data-flux-tooltip] selectors to both button/group.blade.php and input/group/index.blade.php, mirroring the existing [data-flux-input] pattern for two-level nesting:

[&>*:first-child:not(:last-child)>[data-flux-tooltip]>[data-flux-group-target]]:rounded-e-none

This specifically matches the wrapper > tooltip > button pattern using child combinators (>) at each level, so it won't affect buttons nested deep inside menus, dropdowns, or popovers within the group — avoiding the issue with the previous approach of using descendant selectors.

Fixes #2021