Fix 10 known bugs: catalog, single product, and account pages (v0.1.5)

Catalog: page title via woocommerce_page_title(), breadcrumbs, category
template rename (underscore), 3-column grid, single chevron on sort.

Single product: variable form data attributes + disabled CSS class fix
(WC JS only toggles CSS classes, not HTML disabled attribute), dark mode
select specificity (0,5,1) to beat WC's (0,4,3) background shorthand,
gallery main image in thumbnail strip with empty URL guard, related/
upsells setup_postdata for correct global $product, grouped product
loop logic rewrite.

Account: downloads via wc_get_customer_available_downloads().

New: product-gallery.js, sanitize_title filter, wc_setup_product_data()
and wp_reset_postdata() Twig functions, product-thumbnails.html.twig
suppressor. Removed obsolete PLAN.md and SETUP.md.

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

templates/loop/header.html.twig

@@ -2,11 +2,8 @@
  # Product Archive Header (Bootstrap 5 Override)
  #
  # Renders the archive page title and optional description.
- #
- # Expected context:
- #   show_page_title     - Whether to display the title (boolean, filtered)
- #   page_title          - Archive page title string
- #   archive_description - Optional archive description HTML
+ # Calls woocommerce_page_title() directly (matching the PHP template)
+ # because wc_get_template('loop/header.php') passes no context args.
  #
  # WooCommerce PHP equivalent: loop/header.php
  #
@@ -15,9 +12,9 @@
  #}
 
 <header class="woocommerce-products-header mb-4">
-    {% if show_page_title is not defined or show_page_title %}
+    {% if apply_filters('woocommerce_show_page_title', true) %}
         <h1 class="woocommerce-products-header__title page-title mb-2">
-            {{ page_title|default('')|esc_html }}
+            {{ fn('woocommerce_page_title', false)|esc_html }}
         </h1>
     {% endif %}