fix: fix equation rendering by changing the toolchain to mathjax (#493)

* docs: update README and build guide

* fix: escape * and _ inside math to prevent markdown emphasis corruption

* fix: configure MathJax to use TeX (Computer Modern) font

* feat: enhance markdown processing with label and figure collection

* fix: remove duplicate bibliography directives from chapter summaries

References are already handled at the chapter level, so the
:bibliography: directives in summary pages are redundant and cause
rendering issues.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

tools/mdbook_preprocessor.py

@@ -5,9 +5,9 @@ import sys
 from pathlib import Path
 
 try:
-    from tools.prepare_mdbook import build_title_cache, parse_bib, rewrite_markdown
+    from tools.prepare_mdbook import build_title_cache, collect_figure_labels, collect_labels, convert_math_to_mathjax, parse_bib, rewrite_markdown
 except ModuleNotFoundError:
-    from prepare_mdbook import build_title_cache, parse_bib, rewrite_markdown
+    from prepare_mdbook import build_title_cache, collect_figure_labels, collect_labels, convert_math_to_mathjax, parse_bib, rewrite_markdown
 
 
 PLACEHOLDER_PREFIX = "[TODO: src = zh_chapters/"
@@ -43,7 +43,25 @@ def main() -> int:
             for key, fields in parse_bib(extra_bib).items():
                 bib_db.setdefault(key, fields)
 
-    for chapter in iter_chapters(book.get("items", [])):
+    chapters = iter_chapters(book.get("items", []))
+
+    # Pass 1: collect all :label: directives and figure labels
+    ref_label_map: dict[str, str] = {}
+    fig_number_map: dict[str, str] = {}
+    for chapter in chapters:
+        source_path = chapter.get("source_path") or chapter.get("path")
+        if not source_path:
+            continue
+        for label in collect_labels(chapter["content"]):
+            ref_label_map.setdefault(label, source_path)
+        number = chapter.get("number")
+        if number:
+            prefix = ".".join(str(n) for n in number)
+            for idx, label in enumerate(collect_figure_labels(chapter["content"]), 1):
+                fig_number_map[label] = f"{prefix}.{idx}"
+
+    # Pass 2: rewrite markdown with cross-reference linking
+    for chapter in chapters:
         source_path = chapter.get("source_path") or chapter.get("path")
         if not source_path:
             continue
@@ -56,7 +74,11 @@ def main() -> int:
             bibliography_title=BIBLIOGRAPHY_TITLE,
             frontpage_switch_label=FRONTPAGE_SWITCH_LABEL,
             frontpage_switch_href=FRONTPAGE_SWITCH_HREF,
+            ref_label_map=ref_label_map,
+            current_source_path=source_path,
+            fig_number_map=fig_number_map,
         )
+        chapter["content"] = convert_math_to_mathjax(chapter["content"])
 
     json.dump(book, sys.stdout, ensure_ascii=False)
     return 0