Improve list/read command behavior and cleanups

[AdamBuchweitz]

Motivation

• Ensure the list command prints the "books" header only when listing books and not when listing translations.
• Make the numeric column shown for each book reflect the currently selected sort mode (traditional, alphabetical, chronological).
• Simplify and harden chapter and whole-Bible read logic and fix a README typo.

Description

• Update list_books to compute a displayed_position accessor based on the chosen sort_order and use it when rendering the numeric column.
• Move the header print ("The books of the Bible, sorted %sly:") into the Books branch so it is not printed for Translations.
• Simplify build_chapter in lib/commands/cmd_read.ml by removing an unnecessary Option wrapping/fold around chapter content that is always present.
• Replace three repeated Str.global_replace calls with a single regex "\n\n\n+" normalization and remove the temporary List.take 2 cap so full-Bible reads process all fetched books.
• Fix README typo (vreses -> verses).

Testing

• Ran git diff --check which reported no whitespace/format errors and succeeded.
• Searched for patched patterns with rg "List.take 2|vreses|The books of the Bible" which confirmed the intended changes are present.
• Attempted dune build in the environment which failed because dune is not installed, so compilation could not be validated here.

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[chatgpt-codex-connector]

Number books by sorted index, not alphabetical_order

Using item.alphabetical_order as the displayed numeric column makes bible list books --alphabetical output ambiguous, because those values are not unique in the data model (for example, I Samuel and Mark both use 28, and several books share 25 in lib/models/models.ml). This change introduces repeated/missing numbers in the left column, so users can no longer treat it as a position indicator; computing the number from the book's index in the sorted list would keep the column stable and meaningful.

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