Retrieve the full metadata record for a specific LOC digital item. Returns the imprint (place, publisher, and date of publication), contributors, LCSH subject headings and the subject terms the search subject filter accepts, summary, languages, locations, rights information, physical description, call number, original and online formats, access restrictions, former catalog IDs, notes, and related items, plus the item's digital resources (each with its page count, representative image, PDF, and audio) and a window of its pages. Each page has a page_url and has_text; pass a page_url with has_text true to libofcongress_get_newspaper_page to read that page's text (newspaper, book, and manuscript pages alike). A long item lists 50 pages per call: continue with page_offset set to next_page_offset. Set include_files for each listed page's downloadable files (TIFF, JP2, JPEG sizes, text). Use after libofcongress_search_items on a result whose is_item is true. Pass the result id — a simple ID, an LCCN, or a slash-separated newspaper path — or a loc.gov item link (`https://www.loc.gov/item/<id>/`) or LCCN permalink (`https://lccn.loc.gov/<lccn>`), which is read as its id. Non-item results (is_item: false) — collections, exhibits, guides, newspaper pages, catalog.loc.gov records, hdl.loc.gov finding aids — have no item record and cannot be retrieved here.