[ADD] подсветка синтаксиса C и C++ в листингах

tests/test_render.py

@@ -334,7 +334,7 @@ LISTING_MD = (
 def test_listing_with_caption() -> None:
     tex = render(LISTING_MD)
     assert "caption={Потокобезопасная очередь}" in tex
-    assert "language=C++" in tex
+    assert "language=[modern]C++" in tex
     assert "class ThreadSafeQueue {};" in tex
 
 
@@ -350,7 +350,7 @@ def test_listing_caption_paragraph_is_not_duplicated() -> None:
 
 def test_listing_without_caption_stays_bare() -> None:
     tex = render("```cpp\nint main() {}\n```\n")
-    assert "\\begin{lstlisting}[language=C++]" in tex
+    assert "\\begin{lstlisting}[language=[modern]C++]" in tex
     assert "caption=" not in tex
 
 
@@ -369,7 +369,7 @@ def test_paragraph_starting_with_listing_word_is_not_a_caption() -> None:
 def test_listing_language_is_mapped_to_listings_name() -> None:
     """listings не знает 'cpp', только 'C++'."""
     tex = render("```cpp\nint x;\n```\n")
-    assert "language=C++" in tex
+    assert "language=[modern]C++" in tex
 
 
 def test_listing_unsupported_language_falls_back_to_plain() -> None:
@@ -480,3 +480,9 @@ def test_abbreviation_table_has_no_extra_column_padding() -> None:
     """Отбивка между колонками добавляется к \\linewidth и роняет строку за поле."""
     tex = body(render(ABBR_MD))
     assert "@{}p{\\dimexpr\\linewidth" in tex
+
+
+def test_cpp_uses_extended_dialect() -> None:
+    """Встроенный C++ в listings не знает auto, nullptr и override."""
+    tex = body(render("```cpp\nauto x = nullptr;\n```\n"))
+    assert "language=[modern]C++" in tex