fix: add math support

[tylerdave]

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[github-actions]

Docs Site preview: https://964fa568.rockgarden.pages.dev

[claude]

The previously flagged $a increases and $b decreases issue is resolved: allow_space=False rejects any $token as a closing delimiter when the character immediately before it is a space, which covers the vast majority of prose dollar-variable patterns. The new test_dollar_variables_in_prose_not_math test confirms this.

One residual edge case remains (see inline comment), but the implementation is otherwise clean — CDN SRI hashes are present, textContent correctly unescapes HTML entities before passing to KaTeX, and the block class check for display mode is correct.

[claude]

Bug (Previously flagged — partially addressed): allow_space=False fixes the common $a increases and $b decreases case (space before closing $b blocks it), but slash-separated patterns like $HOME/$USER in plain prose are still consumed: the / before $USER is not whitespace, so HOME/ is wrapped as <span class="math inline">. The result with throwOnError: false is a KaTeX error badge rendered inline.

This is narrower than the previously flagged case — it only affects prose where two $identifier tokens are joined by a non-space, non-digit character without backtick quoting. Acceptable as a documented limitation, but worth a note in docs/Markdown Support.md under the Math section (e.g. "Avoid unquoted $var/path patterns in prose; use backticks instead").