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/meta.html.twig

@@ -4,12 +4,7 @@
  # Renders SKU, categories, and tags as a definition list.
  #
  # Expected context:
- #   product - WC_Product object with:
- #     .get_sku()          - SKU string
- #     .get_id()           - Product ID
- #   sku                   - SKU string (fallback)
- #   categories_html       - Pre-rendered category links HTML
- #   tags_html             - Pre-rendered tag links HTML
+ #   product - WC_Product object (from TemplateOverride)
  #
  # WooCommerce PHP equivalent: single-product/meta.php
  #
@@ -17,6 +12,14 @@
  # @since 0.1.0
  #}
 
+{# Compute categories/tags HTML when not passed as context. #}
+{% if categories_html is not defined %}
+    {% set categories_html = fn('wc_get_product_category_list', product.get_id(), ', ') %}
+{% endif %}
+{% if tags_html is not defined %}
+    {% set tags_html = fn('wc_get_product_tag_list', product.get_id(), ', ') %}
+{% endif %}
+
 <div class="product_meta border-top pt-3 mt-3">
     {{ do_action('woocommerce_product_meta_start') }}
 
@@ -26,13 +29,13 @@
             <dd class="col-sm-9">{{ product.get_sku()|esc_html }}</dd>
         {% endif %}
 
-        {% if categories_html is defined and categories_html %}
-            <dt class="col-sm-3 text-body-secondary">{{ __('Categories:') }}</dt>
+        {% if categories_html %}
+            <dt class="col-sm-3 text-body-secondary">{{ fn('_n', 'Category:', 'Categories:', product.get_category_ids()|length, 'woocommerce') }}</dt>
             <dd class="col-sm-9">{{ categories_html|raw }}</dd>
         {% endif %}
 
-        {% if tags_html is defined and tags_html %}
-            <dt class="col-sm-3 text-body-secondary">{{ __('Tags:') }}</dt>
+        {% if tags_html %}
+            <dt class="col-sm-3 text-body-secondary">{{ fn('_n', 'Tag:', 'Tags:', product.get_tag_ids()|length, 'woocommerce') }}</dt>
             <dd class="col-sm-9">{{ tags_html|raw }}</dd>
         {% endif %}
     </dl>