Search a Reddit subreddit

Automatically search a Reddit subreddit on reddit.com. Search posts within a single subreddit, with optional sort and time window, one page at a time. Returns subreddit, count, threads (each with id, url, title, author, score, num_comments, created, subreddit, nsfw, preview_text) and nextCursor: pass it as cursor, with the same subreddit, topic, sort and time, for the next page; it is null on the last page. A search with no matches returns count 0. Reddit ignores `time` when sort=new. When a query has no genuine matches, Reddit's own search sometimes returns a few loosely related posts from the subreddit instead of an empty result, with no way to tell them apart from real hits. Reddit's subreddit-scoped search cards show titles only, so preview_text is null here; for body excerpts use reddit.com/search_reddit with a `subreddit:name` term in the query.