makeDocxBook: the docx blob goes straight to mammoth.convertToHtml
(mammoth unzips internally; the browser entry takes {arrayBuffer}, the
node entry {buffer}). Converted HTML is sectioned at block-element
boundaries into ~150KB chunks (string-level — no DOMParser), giving a
Part N TOC; images inline as data URIs by default.
makeBook: zip files whose entries contain word/document.xml route to
the docx branch before the EPUB fallback (previously they died inside
new EPUB(...) on the missing container.xml).
mammoth is the fork's first runtime dependency: updates and security
fixes flow via semver; the browser-field mappings swap its node unzip
for the browser one; the dynamic import keeps it out of every other
format's path.
