Fetch details, transcript, comments, comment replies, or live chat for a YouTube video. type="details": returns video{id, title, author, description, viewCount, likeCount, durationSec, publishedAt, tags, isLive} and related[]. type="transcript": returns {videoId, language{code, name, isAutoGenerated}, segments[{text, start, duration}], text}. type="comments": returns {videoId, items[{id, text, author, likeCount, replyCount, repliesToken}], continuationToken}. type="replies": pass the repliesToken of a comment as continuationToken to fetch its replies. type="livechat": returns {videoId, status (live|upcoming|replay|chat_disabled|not_live), isLive, concurrentViewers, messages[{id, text, author, authorId, timestampUsec, isOwner, isModerator, isVerified, superChatAmount}], continuationToken, pollIntervalMs}. Set chatType="top" for moderated Top chat (default) or "live" for all messages. To follow a live stream, poll again passing the previous continuationToken for only new messages, waiting pollIntervalMs between polls; a null continuationToken means the stream ended. Best for: extracting content from a known video URL. Not recommended for: discovering videos. Use stophy_search_videos instead.