fix(single): place the video footer breadcrumb like the reference

Drop the invented .post-breadcrumbs wrapper and echo the breadcrumb
inside the reference's flex jsb at row; split .single-video .breadcrumb
out of the cover-overlay rule (-6px pull and opacity reset belong to
title-over-cover contexts only) and restore the legacy 15px footer
padding. Pin the structure in the cover contract test and rebuild the
homepage aggregates.

tests/widget-system/single-cover-height-contract.test.cjs

@@ -123,6 +123,34 @@ test('video cover: play never runs against a sourceless player', () => {
   assert.doesNotMatch(player, /querySelectorAll\('\.switch-video, \.switch-iframe'\)/);
 });
 
+test('video cover: footer breadcrumb sits in the reference flex row', () => {
+  const breadcrumbCss = read('assets/css/frontend/breadcrumb.css');
+  const coverCss = read('assets/css/frontend/single-post/cover.css');
+
+  // 对齐 zibll：footer 里面包屑直接位于 flex jsb at 行，无自造包装层。
+  assert.match(
+    singleRender,
+    /single-video-footer dplayer-featured">\s*\n\s*<div class="flex jsb at">\s*\n\s*<\?php echo \$crumbs;/,
+    '视频 footer 面包屑必须在 flex jsb at 行内直出'
+  );
+  assert.doesNotMatch(
+    singleRender + breadcrumbCss + coverCss,
+    /post-breadcrumbs/,
+    '自造的 .post-breadcrumbs 包装层已死，禁止回归'
+  );
+
+  // 视频面包屑只归零 padding、保留基础弱化样式；-6px 左拉仅属封面叠加层。
+  assert.match(breadcrumbCss, /\.single-video \.breadcrumb \{\s*\n  padding: 0;\s*\n\}/);
+  assert.doesNotMatch(
+    breadcrumbCss,
+    /\.single-video \.breadcrumb,[\s\S]{0,200}margin: 5px 0 0 -6px/,
+    '.single-video 不得并入 -6px 叠加组，否则面包屑贴出左边界'
+  );
+
+  // footer 内边距恢复 legacy 15px 契约，禁止 4px 侧边距覆盖。
+  assert.doesNotMatch(coverCss, /\.single-video-footer \{ padding:/);
+});
+
 test('resource singles get the cover leaf versioned, never via the aggregate @import', () => {
   // 聚合文件的 @import 无版本号：浏览器会拿旧缓存（含已废弃的 .single-cover
   // padding 规则）把封面高度链挤成 0，资源型文章封面直接空白。