fix: add mhchem support to markdown renderer

[aaditmehtacoder]

Description

Adds the KaTeX mhchem contrib import to the GUI markdown renderer so chemistry notation like \ce{H2O} and \pu{...} can render correctly instead of causing KaTeX parsing errors.

Fixes #12561

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Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

Screen recording or screenshot

Tested locally in the VS Code Extension Development Host. The block reaction $$\ce{CO2 + C -> 2 CO}$$ renders successfully as a typeset chemical reaction instead of crashing/stopping the message render.

Tests

Manual testing in the locally-built Continue extension:

• Tested inline chemistry notation with $\ce{H2O}$
• Tested ion notation with $\ce{Fe^{2+}}$
• Tested block reaction rendering with $$\ce{CO2 + C -> 2 CO}$$
• Tested units with $\pu{5 mol}$

Confirmed the message renders without stopping mid-output.

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Summary by cubic

Add katex/contrib/mhchem to the GUI markdown renderer so chemistry notation (\ce{...}, \pu{...}) renders correctly instead of throwing KaTeX parse errors. Fixes #12561.

^{Written for commit dec323a. Summary will update on new commits.}

[github-actions]

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[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}

[aaditmehtacoder]

I have read the CLA Document and I hereby sign the CLA