Draw the connected choice group without Tailwind

Plan step 36. <x-group> renders data-md-group with its size, variant,
shape, multiple and inline, a data-md-button-group row and
data-md-group-segment labels over its radios or checkboxes. group.css
draws the segments as M3's buttons with the toggle button's colours
from :has(:checked), the disabled treatment from :has(:disabled), the
focus ring from :has(:focus-visible) and the 48px target at xs and sm.

The connected shapes move into button-group.css (the corner scale,
square ends, the pressed and selected inner corners), which group.css
imports; <x-button-group> adopts them in its own rewrite. The group's
render tests move to GroupTest; AppBarTest (navigation group) follows
the new legend and row hooks of theme-toggle's rows.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

tests/Feature/Components/ActionStylesheetsTest.php

@@ -15,6 +15,7 @@ dataset('action components', [
     'tooltip',
     'badge',
     'button',
+    'group',
 ]);
 
 it('draws the component from a stylesheet shaped like every package stylesheet', function (string $name) {
@@ -48,7 +49,7 @@ it('writes no class list into the view', function (string $name) {
     $view = File::get(__DIR__."/../../../resources/views/components/{$name}.blade.php");
 
     // A class the caller hands in (`hint-class`, `icon-class`, a slot's attributes) passes through.
-    expect($view)->not->toMatch('/\bclass="(?!\{\{ \$)|@class\(|->class\(|toCssClasses|(?:x-bind)?:class=/');
+    expect($view)->not->toMatch('/(?<![\w-])class="(?!\{\{ \$)|@class\(|->class\(|toCssClasses|(?:x-bind)?:class=/');
 })->with('action components');
 
 it('takes its values from the tokens and its breakpoints in px', function (string $name) {