stbenjam Show reading statistics
Read ../books-library/SKILL.md first to choose the authoritative backend,
then read ../books-library/references/statistics.md.
Calculate reading velocity for the current year and the last 30 and 90 days, monthly pace, total and average pages, longest and shortest books, personal and source-rating distributions, most-read authors, series versus standalone counts, and TBR size, pages, ratings, age, and recent additions. Use the selected backend's date, rating, read, archive, and TBR fields rather than assuming Calibre and Goodreads schemas are interchangeable.
Return a structured report with readable totals, rounded averages, a monthly breakdown, and a few evidence-based insights. Skip records missing required values, report how many were skipped, and do not compare the two backends unless the user explicitly asks and they represent the same library.