Static Bible metadata used by BibleEx.Librarian and other helpers.

This module exposes pure data functions that describe the structure of the Protestant Bible:

• books/0 – full lowercase book names mapped to their canonical number (1–66).
• osis_books/0 – OSIS identifiers mapped to book numbers.
• shortened_books/0 – short forms and liturgical abbreviations mapped to book numbers.
• variants/0 – additional informal or alternate book keys mapped to book numbers.
• book_names/0 – ordered list of name variants (OSIS, abbreviation, full name, short) by book number.
• last_verse/0 – two-dimensional list of last verse numbers per chapter, per book.

All functions are deterministic and side-effect free; they simply return in-memory maps or lists that other modules use for parsing and validating references.