Inline $...$ math does not render correctly

Inline $...$ math does not render correctly. Reported during the theme evaluation in QuantEcon/lecture-python-programming#475 (closed, never merged).

Context. The evaluation built the QuantEcon Python Programming lectures against main at 6a22984 — the current and only HEAD of this repo, which already includes both mathjax commits (fdc28b9 feat: auto-enable sphinx.ext.mathjax in theme setup and 5629fed fix(mathjax): use Sphinx's mathjax3_config instead of raw script tag). So this is not a case of an untested fix: the defect reproduces against the theme's final state.

Preview build: https://699d241d064feca2f249791b--epic-agnesi-957267.netlify.app/intro

Why it matters. Inline math is pervasive across QuantEcon lecture content — this blocks any serious evaluation of the theme on real scientific material. quantecon-book-theme renders the same source correctly, so the source markup is not at fault.

Suggested starting points: confirm mathjax3_config is reaching the rendered page, check whether MathJax's inline delimiters ($...$) are enabled — MathJax 3 disables single-$ inline math by default unless inlineMath is configured — and verify against docs/kitchen-sink.md, which should grow an inline-math case if it lacks one.

Start by inspecting the theme's MathJax setup and confirm whether mathjax3_config reaches the rendered page. Use docs/kitchen-sink.md to add or verify an inline $...$ example, then build the documentation and confirm that single-dollar inline math renders correctly.