test: 覆盖率提升至 100%（fail_under 90→99，13 个防御/边界用例）

tests/test_table_extractor.py

@@ -49,4 +49,20 @@ def test_extract_table_uses_enum_value():
 def test_forward_fill_ignores_invalid_range():
     matrix = [["A"], ["B"]]
     assert forward_fill(matrix, [(0, 1, 2, 1)]) == matrix  # min_row=0 非法 → 不崩溃不改数据
-    assert forward_fill(matrix, [(9, 9, 9, 9)]) == matrix  # 越界 → 不崩溃
+    assert forward_fill(matrix, [(9, 9, 9, 9)]) == matrix  # 越界 → 不崩溃
+
+
+def test_extract_table_empty_matrix():
+    # 空矩阵 → 返回空表（headers/rows 均为空），不崩溃（L 空矩阵分支）
+    table = extract_table("空シート", [], "f.xlsx", SheetType.FUNCTION)
+    assert table.headers == []
+    assert table.rows == []
+
+
+def test_extract_table_header_row_out_of_range():
+    # header_row 越界/负值 → 回落 0（防御分支）
+    mat = [["ID", "名前"], ["1", "田中"]]
+    t_high = extract_table("社員", mat, "f.xlsx", SheetType.FUNCTION, header_row=9)
+    t_neg = extract_table("社員", mat, "f.xlsx", SheetType.FUNCTION, header_row=-1)
+    assert t_high.headers == ["ID", "名前"]
+    assert t_neg.headers == ["ID", "名前"]