Fetch one IEEE Xplore record by its article_number or DOI: full metadata including title, every author with affiliation, the complete abstract, publication venue, year, volume/issue, page range, publisher, IEEE and author index terms, plus standard_number and standard_status when the record is a standard, and the Xplore html_url / pdf_url. Use it to expand a hit from ieee_search or ieee_standard_search, or when an agent already holds an IEEE DOI or article number. Returns metadata plus the abstract; the full text is sold by IEEE — html_url is where to purchase or access it. Requires your own free IEEE Xplore API key via _apiKey (register an app at developer.ieee.org). Example: ieee_article({ article_number: "8766229", _apiKey: "your-ieee-key" }). Example: ieee_article({ doi: "10.1109/IEEESTD.2020.9363693", _apiKey: "your-ieee-key" })