feat: rebuild product detail page to match cms design (tabs/attrs/spec-table)

Task 12a: rebuild product detail to precisely match cms [slug].astro - sticky tab nav (muted bar, brand underline, single-row h-scroll) with .sf-tp-panel/.active switching via inline script (no-JS renders all panels flat); Product Details panel renders body HTML as rich-body with cms table rules (full-width, hairline borders, zebra, inline width/height override, cell div scrub); Specifications panel shows clean spec-table with two key/value pairs per row when specs exist; panel titles get the cms 3px brand underline. Breakpoints mapped cms 900/960 -> platform 900, cms 620 -> 620; product responsive rules consolidated in the 12a block and removed from the shared responsive block. Product title keeps h1 tag at cms h2 scale (2xl) per platform single-h1 contract. Note: most product.html and test edits were swept into concurrent commit 85e6d4a; this commit carries the pro.css 12a block and the h1 refinements.

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

tests/test_theme_registry.py

@@ -212,10 +212,10 @@ def test_trade_pro_product_layout_structure(factory):
     assert media is not None and 'hp-200.jpg' in media.get('src', '')
     thumbs = soup.select('.sf-tp-product-thumbs [data-gallery-image]')
     assert len(thumbs) == 2
-    # 标题区：cms 对齐——产品名 h2（2xl 量级，cms 产品页全页无 h1）+ 询盘 CTA
+    # 标题区：产品名用 cms h2 量级（2xl 非巨型；平台全站单 h1 契约保留 h1）+ 询盘 CTA
     # （/preview/ 响应会把根相对 href 重写为 /preview/{sid}/{bid}/contact/，故用后缀匹配）
-    assert soup.select_one('.sf-tp-product-summary h2.sf-tp-product-title')
-    assert not soup.find_all('h1')  # cms [slug].astro 产品页标题层级从 h2 起
+    assert soup.select_one('.sf-tp-product-summary h1.sf-tp-product-title')
+    assert len(soup.find_all('h1')) == 1  # 平台单 h1 契约（与 test_theme_pro_v3 一致）
     assert soup.select_one('.sf-tp-product-actions a.sf-tp-btn[href$="/contact/"]')
     # 选项卡导航：sticky 容器 + 单行横滚 tabs-row；首个 active，第二个有 specs 才显
     tabs = soup.select('.sf-tp-product-tabs .sf-tp-tabs-row .sf-tp-tab')