Source data wraps every math fragment in display-mode $$ delimiters,
which KaTeX rendered as centered blocks mid-sentence. scripts/fix_math.py
normalizes the corpus: $$/$ pairs become inline \\(...\\) (block
derivations with newlines or environments stay display), legacy
\\matrix blocks become begin/end matrix, _\\limits/^\\limits,
\\raise/\\lower boxes, \\root/\\of, \\tag and \\, are rewritten
to KaTeX-supported forms. Batch-validated 60k inline spans: 99.98% render
clean; remaining handful are source pathologies that degrade to text.
import_examgoal.py runs the same normalization at write time.
