Add buttons, menus and the rest of M3 Expressive's actions

<x-button> (label buttons, icon buttons and toggles in five sizes, with
filled, tonal, outlined, elevated and text variants in any colour role),
<x-tooltip>, <x-menu> with items, groups and separators, <x-button-group>,
<x-group> as a connected button group, <x-split-button>, <x-fab>,
<x-fab-menu> and <x-loading>. Sizes, colours and shapes come from
androidx Compose Material 3's tokens; the loading indicator ports its
Morph into SVG + SMIL.

Menus follow WAI-ARIA's menu button pattern on popovers placed by CSS
anchor positioning. Browser tests run in Chromium, Firefox and WebKit.
The showcase fetches the icon names on demand: inlined, they tripped
Pest's test server into HTTP 431s under Firefox.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy

tests/Feature/Components/SplitButtonTest.php

@@ -0,0 +1,43 @@
+<?php
+
+it('puts the action on the leading button and the menu on the trailing one', function () {
+    $html = (string) $this->blade(<<<'BLADE'
+        <x-split-button label="Download all" icon="download" wire:click="downloadZip" menu-label="Download options" class="mt-4">
+            <x-menu-item label="As a ZIP" />
+        </x-split-button>
+        BLADE);
+
+    expect($html)
+        ->toContain('data-button-group="split"')
+        ->toContain('mt-4')
+        ->toContain('data-split="leading"')
+        ->toContain('wire:click="downloadZip"')
+        ->toContain('data-split="trailing"')
+        ->toContain('aria-label="Download options"')
+        ->toContain('role="menu"')
+        ->toContain('As a ZIP')
+        ->and(substr_count($html, 'wire:click="downloadZip"'))->toBe(1);
+});
+
+it('leaves the corners to the group', function () {
+    $html = (string) $this->blade('<x-split-button label="Save"><x-menu-item label="Draft" /></x-split-button>');
+
+    preg_match_all('/<button\b[^>]*data-split="[^"]*"[^>]*>/', $html, $halves);
+
+    expect($halves[0])->toHaveCount(2);
+
+    foreach ($halves[0] as $half) {
+        expect($half)->not->toContain('rounded-corner-full')->not->toContain('active:rounded-corner');
+    }
+});
+
+it('is filled unless another container variant is asked for', function () {
+    expect((string) $this->blade('<x-split-button label="Save" variant="text"><x-menu-item label="Draft" /></x-split-button>'))->toContain('bg-primary text-on-primary')
+        ->and((string) $this->blade('<x-split-button label="Save" variant="tonal"><x-menu-item label="Draft" /></x-split-button>'))->toContain('bg-secondary-container');
+});
+
+it('gives the two smallest sizes their narrower inner padding and 48px trailing button', function () {
+    expect((string) $this->blade('<x-split-button label="Save" size="xs"><x-menu-item label="Draft" /></x-split-button>'))
+        ->toContain('pe-2.5')
+        ->toContain('w-12');
+});