Name each canonical layout page in its window title

Plan step 38 review: ShowcaseController::layout() passes a title
("List-detail · Layout"), but the frame overwrote it with the section's
own, so all three pages and the Layout overview shared one title. The
frame keeps a title it was given; the layout page test asserts each.

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

resources/views/showcase/layout.blade.php

@@ -6,7 +6,8 @@
 @php
     $sections ??= \NoNameWeb\LivewireMaterial\Showcase\Sections::all();
     $section ??= null;
-    $title = $section !== null ? $sections[$section]['title'] : 'Livewire Material';
+    // A page of a section's own (a canonical layout, ShowcaseController::layout()) names itself.
+    $title ??= $section !== null ? $sections[$section]['title'] : 'Livewire Material';
 
     $destinations = [[
         'title' => 'Overview',