fix(single): match the reference video cover height (bare ratio)

Zibll reserves +50px only for covers whose title overlays them
(image/slide via .single-cover/.single-cover-slide); the video cover
keeps its title in the footer below and uses the bare scale height
(.dplayer-scale-height). Drop the +50px from the video box, pin the
reference height matrix in the contract test, and refresh the stale
slide-action assertion in the toast contract.

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

@@ -1,7 +1,9 @@
 'use strict';
 
-// 文章详情页顶部封面高度契约：单图 / 多图(轮播) / 视频三种模式
-// 必须共用同一高度公式 padding-bottom: calc(比例% + 50px)。
+// 文章详情页顶部封面高度契约（对齐参考主题）：
+// 单图/多图(轮播)封面标题叠加封面，高度 = calc(比例% + 50px)（zibll .single-cover /
+// .single-cover-slide）；视频封面标题在下方 footer、无叠加，高度 = 裸比例%
+// （zibll .dplayer-scale-height）。
 
 const assert = require('node:assert/strict');
 const fs = require('node:fs');
@@ -22,17 +24,18 @@ test('single cover: image mode keeps the calc(scale% + 50px) height', () => {
   );
 });
 
-test('single cover: video mode aligns with the image-mode height formula', () => {
+test('single cover: video mode uses the bare ratio height like the reference dplayer box', () => {
   assert.match(
     singleRender,
-    /single-cover--video imgbox-container" style="padding-bottom:calc\(<\?php echo esc_attr\(\(string\) \$video_scale\); \?>% \+ 50px\);"/,
-    '视频封面必须输出 calc(video_scale% + 50px) 内联高度'
+    /single-cover--video imgbox-container" style="padding-bottom:<\?php echo esc_attr\(\(string\) \$video_scale\); \?>%;"/,
+    '视频封面必须输出裸 video_scale% 高度（标题在下方 footer，无叠加补偿）'
   );
-  // 不得回退到裸比例高度。
+  // +50px 是标题叠加封面的补偿量，仅单图/多图封面适用；视频封面
+  // 对齐参考主题 .dplayer-scale-height，不得继承该公式。
   assert.doesNotMatch(
     singleRender,
-    /padding-bottom:<\?php echo esc_attr\(\(string\) \$video_scale\); \?>%;"/,
-    '视频封面禁止输出不带 +50px 的裸比例高度'
+    /single-cover--video imgbox-container" style="padding-bottom:calc\(/,
+    '视频封面禁止输出 +50px 叠加补偿高度'
   );
 });