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.

inc/helpers/aksrt-single-render.php

@@ -28,10 +28,13 @@ if (!function_exists('aksrt_single_render_cover')) :
 		$title_html = (string) ($ctx['title_html'] ?? esc_html(get_the_title()));
 
 		if ($type === 'video') :
+			// 视频封面高度为裸比例（对齐参考主题 .dplayer-scale-height 契约）：
+			// 标题/面包屑在下方 .single-video-footer，不叠加封面，无 +50px 补偿；
+			// 单图/多图封面标题叠加封面，才需要 calc(scale% + 50px)。
 			?>
 			<div class="single-head-cover">
 				<div class="single-video">
-					<div class="graphic single-cover single-cover--video imgbox-container" style="padding-bottom:calc(<?php echo esc_attr((string) $video_scale); ?>% + 50px);">
+					<div class="graphic single-cover single-cover--video imgbox-container" style="padding-bottom:<?php echo esc_attr((string) $video_scale); ?>%;">
 						<div class="aksrt-video single-cover__player" data-aksrt-video data-src="<?php echo esc_url($ctx['cover_url']); ?>"<?php echo $poster !== '' ? ' data-poster="' . esc_url($poster) . '"' : ''; ?> style="position:absolute;inset:0;width:100%;height:100%;"></div>
 					</div>
 					<div class="single-video-footer dplayer-featured">