fix: fold case in pack checks only where it folds

scripts/packverify.py

@@ -602,7 +602,14 @@ def verify_pack_against_platform(
 
     with zipfile.ZipFile(zip_path, "r") as zf:
         zip_set = set(zf.namelist())
-        zip_lower = {n.lower(): n for n in zip_set}
+        # A case twin stands in for the file only where the platform's
+        # filesystem folds case, as the builder decides: on Lakka bios.col
+        # and BIOS.col are two files two cores open, and either one missing
+        # was counted present through the other.
+        zip_lower = (
+            {n.lower(): n for n in zip_set}
+            if config.get("case_insensitive_fs", False) else {}
+        )
 
         # Auto-detect flat vs nested ZIP
         is_flat = bool(base_dest) and not any(

tests/test_hidden_extras.py

@@ -61,6 +61,21 @@ class OneRule(unittest.TestCase):
         )
 
 
+class TheIntegrityCheckFoldsCaseLikeTheBuilder(unittest.TestCase):
+    """--verify-packs counted a file present through its case twin on Lakka,
+    whose filesystem keeps bios.col and BIOS.col apart: a pack missing one
+    of the two passed step 6."""
+
+    def test_case_folding_reads_the_platform(self):
+        source = (REPO_ROOT / "scripts" / "packverify.py").read_text(encoding="utf-8")
+        compact = " ".join(source.split())
+        self.assertRegex(
+            compact,
+            r"zip_lower = \( \{n\.lower\(\): n for n in zip_set\} "
+            r"if config\.get\(\"case_insensitive_fs\", False\) else \{\} \)",
+        )
+
+
 class TheReportSaysSo(unittest.TestCase):
     """Reads the repository: skips when the database is absent."""