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/single-product/product-thumbnails.html.twig

@@ -0,0 +1,13 @@
+{#
+ # Product Thumbnails (Bootstrap 5 Override)
+ #
+ # Intentionally empty — the product-image.html.twig template renders its own
+ # thumbnail gallery strip using Bootstrap grid. This override suppresses the
+ # default WC output from woocommerce_show_product_thumbnails() which would
+ # render additional full-size gallery images below the thumbnail row.
+ #
+ # WooCommerce PHP equivalent: single-product/product-thumbnails.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.5
+ #}