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Describe the bug:
\providecommand overwrites the existing macro if already defined.

(La)TeX code:

\newcommand{\foo}{a}
\providecommand{\foo}{b}
\foo

Expected behavior:
\providecommand should do nothing if the macro already exists.

QuickLaTeX screenshot:

Screenshots:

Environment (please complete the following information):

• KaTeX Version: 0.16.9
• Device: Desktop
• OS: macOS 14.2.1
• Browser: Firefox
• Version: 122.0.1