feat: refine trade-pro variant pages (brand/service/faq/search/notfound)

Task 11 (layout port finale): rebuild the five thin variant pages in the
sf-tp design language, informed by upstream industrial/automotive
1.3.0/1.4.0 information architecture.

- brand: page-hero (breadcrumb Home > Brands > name, cover bg, anchor
  button) + related-product card grid (fields.brand == page title) +
  brand profile body only when authored; derived placeholder summary
  excluded, empty brands get an empty state, never fabricated intros.
- service: page-hero + 1.2/0.8 detail grid (article-body typography +
  sticky CTA card with contact/back links); empty body collapses to a
  centered solo column with the CTA card kept.
- faq: page-hero + article-body for the rich-text body (platform has no
  faq content type; sanitize strips details/summary so the typography
  layer carries it, block-driven details coexist via sf-canvas) +
  dark contact-guidance card; empty body swaps to an empty state.
- search: adopts the same platform mechanism as all four upstream
  themes (site-runtime.js ?q= client search over dist-root
  search-index.json); #sf-search/#sf-search-results/#sf-search-count
  hooks and .sf-search-page kept as JS contract, panel and injected
  result cards restyled via scoped cms-token overrides.
- notfound: branded dark-band 404 (icon macro, giant 404 h1, English
  copy, back-home + browse-products buttons); no end-cta.

CSS: Task 11 block appended to pro.css (new sf-tp-* classes only, own
900/620 media queries; shared hero/grid/typography responsive rules
come from existing 10a/10c/10d blocks; search overrides beat
factory.css by specificity without touching hooks).

Tests: test_trade_pro_variant_pages_structure covers brand fixture
(related filtering, empty forms), service/faq body-vs-empty, search
mechanism contract + noindex + index asset, 404 structure, v3 spot
checks (single h1, chrome, SVG arrows) and clean build report.

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

themes/trade-pro/pages/brand.html

@@ -1 +1,85 @@
-<section class="pro-inner-hero pro-brand-hero"><div class="pro-wrap pro-brand-hero-grid"><div><span class="pro-eyebrow">BRAND PROFILE / PARTNERS</span><h1>{{page.title}}</h1><p>{{page.summary}}</p></div><div class="pro-brand-media">{{cover(page,'brand')}}</div></div></section><section class="pro-section"><div class="pro-wrap">{{body_copy(content,page)}}{% if related %}{{section_title('PRODUCT LINE','Related products','/products/')}}{{grid(related,'product')}}{% endif %}</div></section>
+{# trade-pro brand detail — 品牌详情精修（Task 11，次要页面收官）。
+   设计参照（本轮无 cms 源对应）：上游 themes/automotive/versions/1.4.0/
+   pages/brand.html 的信息架构——品牌横幅（面包屑 + 眉题/h1/导语 + 页内
+   锚点按钮 + 品牌图）→ 车型/产品网格（section heading + "全部"动作位）→
+   品牌故事（眉题 + h2 + 正文）；industrial 1.3.0 为同构薄形态。本模板以
+   sf-tp 设计语言重组：sf-tp-page-hero（10c 内页 hero：封面底图 + brand-soft
+   罩层）+ sf-tp-section-head/card-grid（10a 卡片系）+ sf-tp-article-body
+   排版层双挂（10d）。
+   数据事实（make_context 对 brand kind）：related = fields.brand 与页题
+   （或 fields.brand 字段）一致的产品/车型集合——品牌页的产品网格只信它；
+   派生品牌页（builder 从产品 brand 字段派生 /brands/<slug>/）body/cover
+   恒空、summary 是平台占位串「相关品牌及产品」——导语按 authored 判定
+   排除占位串（home.html 排除「首页」同款决策），空品牌不虚构介绍：
+   无产品给数据无关的英文导语 + 空态卡，绝不编造品牌故事。
+   面包屑 Brands 链接 /brands/（required_sections 恒保证该路由存在）；
+   hero 锚点按钮锚到 #tp-brand-products（构建器豁免 # 锚点，10h 同款）。 #}
+{% set tp_brand_summary = page.summary if page.summary and page.summary != '相关品牌及产品' else '' %}
+{# 导语优先级：authored 摘要 > 数据派生计数（Jinja 三元与 or 的优先级易误读，
+   显式分行赋值避免歧义）> 空品牌通用引导 #}
+{% if tp_brand_summary %}{% set tp_brand_lead = tp_brand_summary %}
+{% elif related %}{% set tp_brand_lead = ('One product from ' if related|length == 1 else related|length ~ ' products from ') ~ page.title ~ ' — specifications and export documentation included.' %}
+{% else %}{% set tp_brand_lead = 'Products assigned to this brand in the admin console appear here automatically.' %}{% endif %}
+<section class="sf-tp-page-hero sf-tp-brand-hero">
+  {% if safe_image(page.cover) %}<img class="sf-tp-page-hero-bg" src="{{ safe_image(page.cover) }}" alt="" width="1600" height="900" fetchpriority="high" decoding="async">{% endif %}
+  <div class="sf-tp-page-hero-overlay" aria-hidden="true"></div>
+  <div class="wrap">
+    <nav class="sf-tp-breadcrumb" aria-label="Breadcrumb" data-reveal>
+      <a href="/">Home</a><a href="/brands/">Brands</a><span class="sf-tp-breadcrumb-current">{{ page.title }}</span>
+    </nav>
+    <div class="sf-tp-page-hero-copy" data-reveal style="--reveal-i: 1">
+      <span class="eyebrow">BRAND PROFILE / PARTNERS</span>
+      <h1>{{ page.title }}</h1>
+      <p class="sf-tp-page-hero-lead">{{ tp_brand_lead }}</p>
+      {% if related %}<a class="sf-tp-btn" href="#tp-brand-products">View brand products {{ icon('arrow-right') }}</a>{% endif %}
+    </div>
+  </div>
+</section>
+{% if related %}
+<section class="section section--soft sf-tp-brand-products" id="tp-brand-products">
+  <div class="wrap">
+    <div class="sf-tp-section-head" data-reveal>
+      <div>
+        <span class="eyebrow">PRODUCT LINE</span>
+        <h2>{{ page.title }} products</h2>
+      </div>
+      <a class="sf-tp-more" href="/products/">All products {{ icon('arrow-right', cls='sf-tp-icon--sm') }}</a>
+    </div>
+    <div class="sf-tp-card-grid">
+      {% for tp_item in related[:8] %}
+      <article class="sf-tp-card" data-reveal style="--reveal-i: {{ loop.index0 % 4 }}">
+        <div class="sf-tp-card-media">{{ cover(tp_item, 'product') }}</div>
+        <div class="sf-tp-card-body">
+          <h3>{{ tp_item.title }}</h3>
+          <p>{{ (tp_item.summary or 'Published specifications available on request.').split('.')[0] }}.</p>
+          <a class="sf-tp-more" href="{{ safe_href(tp_item.route) }}">View details {{ icon('arrow-right', cls='sf-tp-icon--sm') }}</a>
+        </div>
+      </article>
+      {% endfor %}
+    </div>
+  </div>
+</section>
+{% else %}
+<section class="section sf-tp-brand-empty-section">
+  <div class="wrap">
+    <div class="sf-tp-listing-empty" data-reveal>
+      <h2>No products listed under this brand yet</h2>
+      <p>Products assigned to this brand appear here automatically once published.</p>
+      <a class="sf-tp-btn sf-tp-btn--ghost" href="/products/">Browse all products {{ icon('arrow-right') }}</a>
+    </div>
+  </div>
+</section>
+{% endif %}
+{% if content %}
+<section class="section sf-tp-brand-profile">
+  <div class="wrap">
+    <div class="sf-tp-section-head" data-reveal>
+      <div>
+        <span class="eyebrow">BRAND PROFILE</span>
+        <h2>About {{ page.title }}</h2>
+      </div>
+    </div>
+    <div class="sf-tp-brand-body sf-tp-article-body" data-reveal style="--reveal-i: 1">{{ body_copy(content, page) }}</div>
+  </div>
+</section>
+{% endif %}