Add M3 error pages and the Markdown mail theme

Error pages for 401 to 503 in an error-view root appended to view.paths,
with an inline fallback when the Vite build is missing, and a mail theme
rendered from the application's scheme JSON, with opt-in header and
message components. Completes Phase 9.

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

resources/views/showcase/index.blade.php

@@ -26,5 +26,6 @@
         @include('livewire-material::showcase.sections.bars')
         @include('livewire-material::showcase.sections.navigation')
         @include('livewire-material::showcase.sections.data')
+        @include('livewire-material::showcase.sections.pages')
     </main>
 @endsection

resources/views/showcase/layout.blade.php

@@ -18,7 +18,7 @@
                 <a href="{{ route('livewire-material.showcase') }}" class="shrink-0 type-title-lg max-sm:hidden">Livewire Material</a>
 
                 <nav class="-my-2 flex min-w-0 flex-1 gap-x-4 overflow-x-auto py-2 whitespace-nowrap type-label-lg text-on-surface-variant [scrollbar-width:none]" aria-label="Sections">
-                    @foreach (['colour' => 'Colour', 'type' => 'Type', 'shape' => 'Shape', 'elevation' => 'Elevation', 'motion' => 'Motion', 'icons' => 'Icons', 'buttons' => 'Buttons', 'menus' => 'Menus', 'communication' => 'Communication', 'progress' => 'Progress', 'containment' => 'Containment', 'carousel' => 'Carousel', 'fields' => 'Fields', 'chips' => 'Chips', 'sliders' => 'Sliders', 'pickers' => 'Date pickers', 'timepickers' => 'Time pickers', 'bars' => 'Bars', 'navigation' => 'Navigation', 'data' => 'Data'] as $anchor => $section)
+                    @foreach (['colour' => 'Colour', 'type' => 'Type', 'shape' => 'Shape', 'elevation' => 'Elevation', 'motion' => 'Motion', 'icons' => 'Icons', 'buttons' => 'Buttons', 'menus' => 'Menus', 'communication' => 'Communication', 'progress' => 'Progress', 'containment' => 'Containment', 'carousel' => 'Carousel', 'fields' => 'Fields', 'chips' => 'Chips', 'sliders' => 'Sliders', 'pickers' => 'Date pickers', 'timepickers' => 'Time pickers', 'bars' => 'Bars', 'navigation' => 'Navigation', 'data' => 'Data', 'pages' => 'Pages'] as $anchor => $section)
                         <a href="#{{ $anchor }}" class="rounded-corner-xs hover:text-on-surface focus-ring">{{ $section }}</a>
                     @endforeach
                 </nav>

resources/views/showcase/mail.blade.php

@@ -0,0 +1,40 @@
+{{-- The showcase's sample Markdown mail: every part the theme styles — heading, prose, bold,
+     a list, the button, a panel, a table, subcopy and the footer slot. Markdown, so it stays
+     unindented. --}}
+<x-mail::message>
+# Your export is ready
+
+Hello Anna, the report you asked for on **Monday** has finished. It holds three files and stays available for seven days.
+
+<x-mail::button :url="url('/')">
+Download the export
+</x-mail::button>
+
+<x-mail::panel>
+Files are deleted automatically once they expire. Download them before **20 September** to keep a copy.
+</x-mail::panel>
+
+<x-mail::table>
+| File | Rows | Size |
+|:-----|-----:|-----:|
+| customers.csv | 1,204 | 184 KB |
+| orders.csv | 8,930 | 1.2 MB |
+| summary.pdf | — | 96 KB |
+</x-mail::table>
+
+What happens next:
+
+1. Open the export from the button above.
+2. Check the summary before you share it.
+
+Thanks,<br>
+{{ config('app.name') }}
+
+<x-slot:subcopy>
+If the button does not work, paste this address into your browser: [{{ url('/') }}]({{ url('/') }})
+</x-slot:subcopy>
+
+<x-slot:footer>
+© {{ date('Y') }} {{ config('app.name') }} · [Privacy]({{ url('/') }}) · [Unsubscribe]({{ url('/') }})
+</x-slot:footer>
+</x-mail::message>

resources/views/showcase/sections/pages.blade.php

@@ -0,0 +1,16 @@
+<section id="pages" class="scroll-mt-24 space-y-6">
+    <h2 class="type-headline-md">Pages</h2>
+
+    <p class="max-w-3xl type-body-md text-on-surface-variant">
+        The error pages, raised for real so an app's own <code>resources/views/errors</code> still wins, and the Markdown mail theme
+        (<code>livewire-material::mail.theme</code>) on a sample mail, both in this application's scheme.
+    </p>
+
+    <div class="flex flex-wrap items-center gap-2">
+        @foreach (['401', '402', '403', '404', '419', '429', '500', '503'] as $code)
+            <x-button :link="route('livewire-material.error', $code)" :label="$code" variant="tonal" no-wire-navigate />
+        @endforeach
+
+        <x-button :link="route('livewire-material.mail')" label="Sample mail" icon="mail" variant="outlined" no-wire-navigate />
+    </div>
+</section>