fix: enable inline math rendering in mdbook

tests/test_mdbook_mathjax.py

@@ -0,0 +1,56 @@
+from __future__ import annotations
+
+import shutil
+import subprocess
+import tempfile
+import unittest
+from pathlib import Path
+
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+THEME_HEAD = REPO_ROOT / "theme" / "head.hbs"
+
+
+class MdBookMathJaxTests(unittest.TestCase):
+    def test_custom_head_enables_inline_dollar_math_before_mathjax_script(self) -> None:
+        if shutil.which("mdbook") is None:
+            self.skipTest("mdbook is not installed")
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = Path(tmpdir)
+            src = root / "src"
+            theme = root / "theme"
+            src.mkdir()
+            theme.mkdir()
+
+            (root / "book.toml").write_text(
+                """[book]
+title = "Test Book"
+language = "zh-CN"
+src = "src"
+
+[build]
+build-dir = "book"
+
+[output.html]
+mathjax-support = true
+""",
+                encoding="utf-8",
+            )
+            (src / "SUMMARY.md").write_text("# Summary\n\n- [Chapter](chapter.md)\n", encoding="utf-8")
+            (src / "chapter.md").write_text("# Chapter\n\nInline math $C$.\n", encoding="utf-8")
+            theme_head = THEME_HEAD.read_text(encoding="utf-8")
+            (theme / "head.hbs").write_text(theme_head, encoding="utf-8")
+
+            subprocess.run(["mdbook", "build", str(root)], check=True, capture_output=True, text=True)
+
+            output = (root / "book" / "chapter.html").read_text(encoding="utf-8")
+            config_index = output.index("MathJax.Hub.Config")
+            script_index = output.index("MathJax.js?config=TeX-AMS-MML_HTMLorMML")
+
+            self.assertIn("inlineMath: [['$', '$'], ['\\\\(', '\\\\)']]", output)
+            self.assertLess(config_index, script_index)
+
+
+if __name__ == "__main__":
+    unittest.main()

theme/head.hbs

@@ -0,0 +1,10 @@
+<script type="text/x-mathjax-config">
+MathJax.Hub.Config({
+  tex2jax: {
+    inlineMath: [['$', '$'], ['\\(', '\\)']],
+    displayMath: [['$$', '$$'], ['\\[', '\\]']],
+    processEscapes: true,
+    processEnvironments: true
+  }
+});
+</script>