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

tests/test_formatting_detector.py

@@ -59,4 +59,58 @@ def test_cell_comment_returns_obj():
 
 def test_collect_comments():
     comments = collect_comments(make_wb().active, "f.xlsx")
-    assert len(comments) == 1
+    assert len(comments) == 1
+
+
+def test_to_rgb_hex_accepts_6_digit_hex():
+    from types import SimpleNamespace
+    from genesis.parsers.formatting_detector import _to_rgb_hex
+    assert _to_rgb_hex(SimpleNamespace(rgb="FF3333")) == "FF3333"
+    assert _to_rgb_hex(SimpleNamespace(rgb="00FF00FF")) == "00FF00FF"
+
+
+def test_to_rgb_hex_rejects_black_and_theme():
+    from types import SimpleNamespace
+    from genesis.parsers.formatting_detector import _to_rgb_hex
+    # 纯黑（默认色）与主题色（rgb 为空/异常/非 hex）→ None
+    assert _to_rgb_hex(SimpleNamespace(rgb="00000000")) is None
+    assert _to_rgb_hex(SimpleNamespace(rgb="FF000000")) is None
+    assert _to_rgb_hex(SimpleNamespace(rgb="")) is None
+    assert _to_rgb_hex(SimpleNamespace(rgb="ZZZZZZ")) is None
+    assert _to_rgb_hex(SimpleNamespace(rgb="FFFFF")) is None  # 长度不足
+
+
+class _ExplodingRgb:
+    @property
+    def rgb(self):
+        raise Exception("boom")
+
+
+def test_to_rgb_hex_rgb_access_exception_returns_none():
+    from genesis.parsers.formatting_detector import _to_rgb_hex
+    # L15-16：color.rgb 访问抛异常 → 返回 None（防御分支）
+    assert _to_rgb_hex(_ExplodingRgb()) is None
+
+
+def test_cell_formatting_fills_only_color():
+    from copy import copy
+    from openpyxl.styles import PatternFill
+    from genesis.parsers.formatting_detector import cell_formatting
+    wb = Workbook()
+    ws = wb.active
+    ws["A1"] = "x"
+    # 仅背景色（无 strikethrough / 无字体色）→ 返回 CellFormatting 含 bg_color
+    f = copy(ws["A1"].fill)
+    f.fgColor = PatternFill(start_color="00CC00").fgColor
+    ws["A1"].fill = f
+    fmt = cell_formatting(ws["A1"])
+    assert fmt is not None
+    assert fmt.bg_color is not None
+
+
+def test_cell_formatting_fill_none_branch():
+    # 覆盖 L31 防御分支：fill 为 None（无样式对象）时直接返回 None
+    from types import SimpleNamespace
+    from genesis.parsers.formatting_detector import cell_formatting
+    fake = SimpleNamespace(font=SimpleNamespace(strike=False), fill=None)
+    assert cell_formatting(fake) is None