extract_urls() stripped any trailing ')' unconditionally via
`re.sub(r'[.,;:!?\)]+$', '', url)`. That corrupts URLs that legitimately
end in a parenthesis — most commonly Wikipedia disambiguation links like
https://en.wikipedia.org/wiki/Python_(programming_language), which became
...Python_(programming_language and then 404 when fetched by the web/research
tools.
Strip trailing sentence punctuation as before, but only drop a ')' when it is
unbalanced (more ')' than '('), so a prose-glued "(see https://example.com)"
still loses its closing paren while balanced URLs keep theirs.
Added tests/test_extract_urls.py covering balanced, unbalanced, nested, and
trailing-punctuation cases.
Mazen Tamer Salah