feat: port cms product detail layout into trade-pro (gallery/specs/inquiry)

Rewrite pages/product.html from the 3-row skeleton to the cms
[slug].astro design: breadcrumb -> gallery (main + scrolling thumbs,
reusing the platform pro.js data-gallery-image hooks, zero new JS) +
summary column (eyebrow/h1/lead/brand+model/actions) -> flattened
Product details panel -> Specifications table from fields (hidden when
empty) -> related products on the home card grid -> inquiry section
(left contact info, right external form only when form_endpoint is
configured, CTA to /contact/ otherwise).

Component CSS lands in pro.css under .sf-theme-trade-pro with
900/620 breakpoints; stale .pro-specs tint rules removed (other
themes keep their pro-base skeleton); cross-theme skeleton assertion
in test_theme_pro_v3.py now excludes trade-pro; new
test_trade_pro_product_layout_structure covers the build output.

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

tests/test_theme_pro_v3.py

@@ -19,7 +19,10 @@ def test_complete_theme_families_have_distinct_markup(factory):
             assert soup.find('footer',class_='pro-footer')
             assert len(soup.find_all('h1'))==1,(theme,page_type,len(soup.find_all('h1')))
             assert 'pro-base.css' in r.text and 'pro.js' in r.text
-            if page_type=='product':assert soup.select_one('.pro-product-layout .pro-specs')
+            # trade-pro 的产品详情自 Task 10b 起为 cms 移植布局（sf-tp-product-*），
+            # 骨架断言只覆盖其余沿用 pro-base 骨架的主题（test_theme_registry.py
+            # 的 test_trade_pro_product_layout_structure 覆盖 trade-pro 侧）。
+            if page_type=='product' and theme!='trade-pro':assert soup.select_one('.pro-product-layout .pro-specs')
             if page_type=='listing':assert soup.select_one('[data-pro-filter-search]')
             if page_type=='article':assert soup.select_one('.pro-article-hero')
         main.append(factory.get(f'/api/factory/themes/{theme}/preview?page_type=home').text)