feat: port cms listing layout into trade-pro (kind-branched cards/filters/pagination)

Task 10c. listing.html (category.html now includes it) replaces the thin
pro-inner-hero variant with the cms list designs:
- product-like listings (product/vehicle/brand/case/service) get the
  products/[...page].astro form: ported PageHero, 260px sticky category
  side panel, 3-col sf-tp-card grid reusing the 10a card components
- post-like listings (/news/, /post/) get the news/[...page].astro form:
  1fr+310px two-col layout, horizontal news rows (290px media + tag/
  title/summary/Read more), three aside boxes (Latest/Popular/count)
- pagination is the cms Pagination window (first/last + current-2..+2,
  ellipsis collapse) with arrow-left/arrow-right SVG icons and
  builder-consistent URLs (page 1 = section root)
- platform filter contract kept: .pro-filter-panel stays the immediate
  previous sibling of .pro-filter-scope (pro.js previousElementSibling
  lookup); cards/rows carry .pro-card + data-brand/data-category
- empty sections hide filters/grid/pagination behind a friendly empty
  state (noindex scaffold pages)

Test: test_trade_pro_listing_layout_structure drives a real build with
105 imported products + 3 posts, asserting both branches, static
pagination on /categories/pumps/ pages 1-2, contract adjacency, and
no bare arrow glyphs.

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

themes/trade-pro/pages/category.html

@@ -1,2 +1,4 @@
-<section class="pro-inner-hero pro-listing-hero"><div class="pro-wrap"><span class="pro-eyebrow">DISCOVER / {{'CATEGORY' if kind=='category' else 'COLLECTION'}}</span><h1>{{page.title}}</h1><p>{{page.summary or 'Browse all published content in this section.'}}</p><div class="pro-breadcrumb"><a href="/">Home</a><span>／</span><strong>{{page.title}}</strong></div></div></section>
-<section class="pro-section pro-list-section"><div class="pro-wrap">{{ filters() }}<div class="pro-filter-scope">{{grid(listing,'catalog')}}</div>{% if pagination and pagination.pages>1 %}<nav class="pro-pages-nav" aria-label="Catalogue pagination">{% if pagination.previous %}<a href="{{pagination.previous}}" rel="prev">{{ icon('arrow-left') }} Previous</a>{% endif %}<span>Page {{pagination.page}} of {{pagination.pages}}</span>{% if pagination.next %}<a href="{{pagination.next}}" rel="next">Next {{ icon('arrow-right') }}</a>{% endif %}</nav>{% endif %}</div></section>
+{# 派生分类页与 listing 同构（Task 10c 起共用同一列表布局；
+   分类上下文由 theme_pro.select_listing 按 page.category 过滤产品组，
+   分页来自构建期 render_paginated 的 _pagination）。 #}
+{% include 'pages/listing.html' %}