test(docx): add unit tests for list counter, enum marker, and sequence reset helpers

  Adds test_list_counter_and_enum_marker covering helper methods introduced
  in the list numbering fix: counter increment, sub-level reset on parent
  advance, hierarchical marker building, and selective sequence reset.

Signed-off-by: Emre Çalışır <emrecalisir95@gmail.com>

Author: emreclsr

tests/test_backend_msword.py

@@ -392,3 +392,44 @@ def test_get_heading_and_level_non_heading(
     label, level = backend._get_heading_and_level(style_label)
     assert label == expected_label
     assert level == expected_level
+
+
+def test_list_counter_and_enum_marker(docx_paths):
+    """Test list counter increment, sub-level reset, marker building, and sequence reset."""
+    docx_path = docx_paths[0]
+    in_doc = InputDocument(
+        path_or_stream=docx_path,
+        format=InputFormat.DOCX,
+        backend=MsWordDocumentBackend,
+    )
+    backend = in_doc._backend
+
+    # Basic increment
+    assert backend._get_list_counter(1, 0) == 1
+    assert backend._get_list_counter(1, 0) == 2
+    assert backend._get_list_counter(1, 1) == 1
+    assert backend._get_list_counter(1, 1) == 2
+    assert backend._get_list_counter(1, 1) == 3
+
+    # Advancing parent level resets sub-levels
+    backend._get_list_counter(1, 2)  # (1,2) = 1
+    backend._get_list_counter(1, 0)  # (1,0) = 3, resets lvl 1 and 2
+    assert backend.list_counters[(1, 1)] == 0
+    assert backend.list_counters[(1, 2)] == 0
+    assert backend._get_list_counter(1, 1) == 1  # restarts from 1
+
+    # Hierarchical enum markers
+    backend.list_counters[(1, 0)] = 2
+    backend.list_counters[(1, 1)] = 3
+    backend.list_counters[(1, 2)] = 1
+    assert backend._build_enum_marker(1, 0) == "2."
+    assert backend._build_enum_marker(1, 1) == "2.3."
+    assert backend._build_enum_marker(1, 2) == "2.3.1."
+    assert backend._build_enum_marker(99, 0) == "1."  # missing counter defaults to 1
+
+    # Reset sequence for a specific numid
+    backend._get_list_counter(2, 0)  # (2,0) = 1
+    backend._reset_list_counters_for_new_sequence(1)
+    assert backend.list_counters[(1, 0)] == 0
+    assert backend.list_counters[(1, 1)] == 0
+    assert backend.list_counters[(2, 0)] == 1  # unaffected