Fix math delimiter and currency handling in chat responses

[jlee600]

Summary

Extends the existing KaTeX renderer to handle \(...\), \[...\], and recognizable equations inside bare parentheses/brackets.

Preserves currency such as $50 and $61.75 alongside existing $...$ math. Keeps Markdown formatting, code, links, and suggested questions intact. Malformed math remains readable without breaking the renderer.

File changes

• src/renderer/src/MessageText.tsx
  Registers the new math plugin alongside the existing Markdown and KaTeX plugins.

• src/renderer/src/remark-model-math.ts
  Adds delimiter detection and currency handling. Protects code and links, then passes recognized equations to the existing KaTeX pipeline.

• tests/unit/typescript/message-text.test.mjs
  Updates the test setup to load the plugin and adds six regression tests for delimiters, currency, mixed formatting, code preservation, and malformed input.

No dependency, retrieval, calculation, prompt, or chat history changes.

Validation

• All 134 TypeScript tests passed.
• Both typechecks and the production build passed.
• git diff --check passed.

Before

After

[Crysta1ightning]

Would matching bare () and [] be too broad? For example, a model could output (2024–2025) as a year range, which the current heuristic would render as math.

Have we observed model responses using bare delimiters that explicit \(...\), \[...\], and the existing $...$ / $$...$$ support do not cover? If not, I would prefer limiting conversion to explicit delimiters.