Make monospace spans code spans only in the docx import and src.

The docx span cleanup now turns every monospace run into a code span
without bold or italic. Whitespace between two code runs joins them, so
"record" and "of" become `record of`. Edge spaces leave the span and
inner runs of spaces collapse. Bold punctuation next to a code span
loses its bold.

The Markdown in src/ is cleaned with the same rule. Fenced blocks are
unchanged. Chapter 6 keeps the removal of two empty list items.

Co-authored-by: Cursor <cursoragent@cursor.com>