fix: added a normalization step for MathJax-style \[\] and \(\) delimiters

[ServeurpersoCom]

So inline and block equations are converted before KaTeX rendering, enabling proper display of model-generated LaTeX in the WebUI:

• Added a dedicated remarkMathJaxDelimiters plugin that rewrites MathJax bracket delimiters into KaTeX-friendly dollar math while limiting the normalization to text nodes so code blocks and other literals remain untouched.

• Wired the new plugin into the existing Markdown processor ahead of remark-math and dropped the prior global string replace, keeping the established remark/rehype pipeline intact while still rendering centered and inline equations correctly.

Missing stage in #16505 because of KaTeX

Close #16598

[ServeurpersoCom]

Raw default output for many model :

Result with this PR :

KaTeX-vs-MathJax.mp4

[ServeurpersoCom]

Sorry for the spam : I had two versions coexisting in my Git history, so I reverted to the simple version that works on its own, without the remark plugin.

[ggerganov]

This patch renders correctly mathematical expressions on my end.

Just a minor note - probably the "Show raw LLM output" option should not be located in the "Reasoning" tab. And the name should be shortened to just "Show raw LLM output".

[ServeurpersoCom]

I realized it and told Alek on discord:D

Because we should group all the debug options into a dedicated developer section, since we’re going to add toolcall debugging soon.
And also "Custom JSON parameters to send to the API. Must be valid JSON format." -> Debug or Developer...
And eventually, the “Advanced” section could be renamed to “Sampling.”
And current "Sampler" inside "Sampling"
What do you think?