Add Bootstrap 5 single product page layout

Add two-column responsive grid (image gallery + product summary) for
single product pages, following the same bridge pattern used for
product archives.

Key changes:
- Create content-single-product.php bridge and Twig layout template
- Add single product renderer at template_redirect priority 11
- Disable WooCommerce block compatibility layer that strips classic
  hooks when parent theme has theme.json
- Move PHP templates to woocommerce/ subfolder for cleaner structure
- Fix Twig templates to self-compute context data not passed by
  wc_get_template() (tabs, short-description, meta, rating)
- Fix Underscore.js triple-brace syntax conflict in variation template
  by wrapping in {% verbatim %}

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

templates/single-product/short-description.html.twig

@@ -2,7 +2,8 @@
  # Product Short Description (Bootstrap 5 Override)
  #
  # Expected context:
- #   short_description - Product short description HTML
+ #   product           - WC_Product object (from TemplateOverride)
+ #   short_description - Product short description HTML (optional)
  #
  # WooCommerce PHP equivalent: single-product/short-description.php
  #
@@ -10,7 +11,12 @@
  # @since 0.1.0
  #}
 
-{% if short_description is defined and short_description %}
+{# Compute short description when not passed as context. #}
+{% if short_description is not defined %}
+    {% set short_description = apply_filters('woocommerce_short_description', product.get_short_description()) %}
+{% endif %}
+
+{% if short_description %}
     <div class="woocommerce-product-details__short-description lead text-body-secondary mb-3">
         {{ short_description|raw }}
     </div>