_extract_verbatim_content only skipped an optional [...] after \begin{env}, using a non-greedy \[.*?\]. Two cases leaked markup into the code item:

• minted takes a mandatory language argument, which became the first line of the code: \begin{minted}{python} gave {python}\nx = 1.
• An lstlisting option value containing ], such as caption={A [nested] cap}, ended the option match early and left cap}] in the code.

The pattern now skips an optional argument whose {...} values may contain brackets, and, for minted only, the {language} argument after it. verbatim, plain lstlisting, multi-line options, and code that itself starts with [ or { behave as before.

The new parametrized test covers minted with and without options and lstlisting with a bracketed caption, with an indented code line so the first-line indentation from #4502 stays covered. It fails on main and passes with this change; the other LaTeX tests pass unchanged.

Using minted's language (or lstlisting's language=) as the code item's language is left for a follow-up.

Issue resolved by this Pull Request:
Resolves #4542

Checklist:

• Documentation has been updated, if necessary. (not needed)
• Examples have been added, if necessary. (not needed)
• Tests have been added, if necessary.