fix: math parsing hangs webchat

[OEvgeny]

Fixes

Changelog Entry

Fixed

• Fixed math parsing that could cause Web Chat to hang when processing certain LaTeX expressions, in PR #5377, by @OEvgeny

Description

This PR addresses a critical issue where Web Chat could hang when parsing certain LaTeX mathematical expressions. The problem occurred specifically when processing escaped sequences in math blocks, particularly affecting expressions with trailing backslashes or incomplete delimiters.

Design

We don't process escape sequences, unless it's an end delimiter. Otherwise we hand processing over to the content state processor which will properly handle line breaks and such.

Specific Changes

• Renamed escaped function to maybeCloseDelimeter for better clarity of intent
• Removed redundant character consumption in escape sequence handling
• Added test case for LLM-generated math expressions with trailing backslashes

-

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)