Exploration: Marked + React Renderer

[dhruvisompura]

Follow up to PR #11212 that explores being able to directly render React components from markdown as suggested by @seeM in this comment: #11212 (review)!

Right now we do Markdown → Tokens → HTML String → DOM, which means we're generating HTML strings and then parsing them back into the DOM. In this PR we now do Markdown → Tokens → React Elements. The main idea is to skip the intermediate HTML string step and work directly with React components. We use Marked to get the tokenized version of the markdown and then pass the tokens to a custom renderer which converts the tokens to the appropriate react component.

That said, there are still a few cases where we need HTML parsing. KaTeX (for LaTeX math) and our syntax highlighting both return HTML strings rather than tokens, so we still use safeSetInnerHtml for those and convert the resulting DOM to React via domToReact.tsx utility (this is pretty close to what we were doing prior to this change but we needed a parser that could better handle katex html unlike htmlParser.ts).

The TokenMarkdownRenderer class handles the token-to-React conversion, with custom components like KatexMath, SyntaxHighlightedCode, and RawHtml for the more complex rendering scenarios.

One benefit of this approach as mentioned by @seeM is allowing us to easily create/explore richer markdown output.

Release Notes

New Features

• N/A

Bug Fixes

• N/A

QA Notes

@:positron-notebooks

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical @:positron-notebooks

^{readme  valid tags}

[seeM]

Code changes look great! I'll take it for a spin locally tomorrow morning, haven't had a chance yet

The base branch was changed.