Instead of using Data.Generics `everywhere` to traverse the entire XML
tree when setting language attributes, navigate directly to the known
path w:docDefaults/w:rPr/w:lang. This is more efficient and removes the
dependency on Data.Generics (mkT, everywhere).
The new `modifyAtPath` helper function takes a list of predicates that
match element names at each level of the path and modifies only the
target element.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
