Fix unstyled pages: rename base.html.twig to avoid parent collision

The child's templates/base.html.twig was shadowing the parent's
views/base.html.twig (full HTML page shell) because prependPath()
made Twig find the child's minimal wrapper first. Rename to
wc-base.html.twig so the parent's page shell renders correctly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/layouts/single.html.twig

@@ -9,7 +9,7 @@
  # @since 0.1.0
  #}
 
-{% extends "base.html.twig" %}
+{% extends "wc-base.html.twig" %}
 
 {% block content %}
     <article>