refactor: count every run line from one tally

The run header, the menu, its game data split and g, the plan, the
screen's plan and game data row and both results now divide one tally
of the list the run keeps. Case variants were counted on the run and
missing from the screen's split, g counted the whole list under a head
narrowed by c, and the result left out the data tree files. The wiki
examples come from real runs of 2026-10-27.

tests/test_doc_pages.py

@@ -98,8 +98,30 @@ class InstallerOutputExample(unittest.TestCase):
                 self.assertIn(part.rsplit(":", 1)[0], install.OMISSION_REASONS.values())
         count, size = re.search(r"\n  (\d+) files \(([\d.]+ [KMG]B)\)", run).groups()
         self.assertIn(f"0/{count} present", run)
-        menu = re.search(r"RetroArch: (\d+) files, ([\d.]+ [KMG]B)\.", text)
-        self.assertEqual(menu.groups(), (count, size))
+        self.assertSplitAddsUp(run, count, size)
+        menu = re.search(r"RetroArch: (\d+) files, ([\d.]+ [KMG]B)[.,]([^`]*)", text)
+        self.assertEqual(menu.groups()[:2], (count, size))
+        self.assertSplitAddsUp(menu.group(3), count, size)
+        games = re.search(r"g\) leave out the (\d+) game data files \(([\d.]+ [KMG]B)\)",
+                          menu.group(3))
+        self.assertIsNotNone(games, "the menu offers to leave the game data out")
+        split = re.search(r"(\d+) BIOS files \(([\d.]+ [KMG]B)\) and (\d+) game data files "
+                          r"\(([\d.]+ [KMG]B)\)", menu.group(3))
+        self.assertEqual(games.groups(), split.groups()[2:])
+
+    def assertSplitAddsUp(self, text: str, count: str, size: str) -> None:
+        """The run counted 8069 files where its menu counted 3259 BIOS files
+        and 5089 game data files: the parts add up to the total they divide,
+        the sizes within the rounding of their three figures."""
+        split = re.search(r"(\d+) BIOS files \(([\d.]+) ([KMG]B)\) and (\d+) game data "
+                          r"files \(([\d.]+) ([KMG]B)\)", text)
+        self.assertIsNotNone(split, "a categorized list says its BIOS files and game data")
+        bios, bios_size, bios_unit, games, game_size, game_unit = split.groups()
+        self.assertEqual(int(bios) + int(games), int(count))
+        units = {"KB": 1, "MB": 1024, "GB": 1024 ** 2}
+        total, unit = size.split()
+        added = (float(bios_size) * units[bios_unit] + float(game_size) * units[game_unit])
+        self.assertLessEqual(abs(added - float(total) * units[unit]), 0.15 * units[unit])
 
 
 class OneResolutionChain(unittest.TestCase):