feat(video): add autoplay and dynamic video loading

- Add autoplay attribute to video player
- Implement dynamic calculation of needed regular videos based on window height
- Update video comments with Japanese content and remove default avatars

js/video.js

@@ -91,10 +91,37 @@ function loadRelatedVideos(currentVideo) {
   shuffleArray(otherRegularVideos);
   
   const selectedShorts = [...sameCategoryShorts, ...otherShorts].slice(0, 3);
-  const selectedRegularVideos = [...sameCategoryRegularVideos, ...otherRegularVideos].slice(0, 10);
+  
+  // Calculate needed regular videos based on page height
+  const calculateNeededVideos = () => {
+    const windowHeight = window.innerHeight;
+    const relatedSection = document.querySelector('.related-videos-section');
+    const shortsSection = document.querySelector('.shorts-section');
+    
+    if (!relatedSection || !shortsSection) {
+      return 10; // Default to 10 if elements not found
+    }
+    
+    const shortsHeight = shortsSection.offsetHeight;
+    const availableHeight = windowHeight - shortsHeight - 48; // 48px for padding/gap
+    
+    // Estimate height per regular video item (including gap)
+    const estimatedVideoHeight = 100; // Average height of each video item
+    
+    // Calculate needed videos
+    const neededVideos = Math.ceil(availableHeight / estimatedVideoHeight);
+    
+    // Ensure we don't exceed available videos
+    const totalAvailableVideos = sameCategoryRegularVideos.length + otherRegularVideos.length;
+    return Math.min(neededVideos, totalAvailableVideos);
+  };
+  
+  const neededVideosCount = calculateNeededVideos();
+  const selectedRegularVideos = [...sameCategoryRegularVideos, ...otherRegularVideos].slice(0, neededVideosCount);
   
   console.log('Selected shorts:', selectedShorts.length);
-  console.log('Selected regular videos:', selectedRegularVideos.length);
+  console.log('Selected regular videos:', selectedRegularVideos.length, '(needed:', neededVideosCount, ')');
+  console.log('Window height:', window.innerHeight);
   
   selectedShorts.forEach(short => {
     const shortElement = document.createElement('div');