fix: raise on a registry missing a platform file

list_registered_platforms skipped a registered platform whose YAML was missing and returned an empty list without a registry. verify --all --strict, every --all build, the CI matrix and the site then ran over fewer platforms and exited 0, and install.py kept serving the stale manifest. Both now raise and name the file.

tests/test_audit_regressions.py

@@ -5355,5 +5355,24 @@ class ThePackCheckAppliesTheFrontendRule(unittest.TestCase):
                 self.assertIsNotNone(_check_member_hash(zf, "bios/x.bin", entry, "md5"))
 
 
+class ABrokenRegistryIsNotAnEmptyOne(unittest.TestCase):
+    """A registered platform whose YAML was renamed was skipped without a
+    word, and a missing registry read as no platforms: verify --all --strict
+    and every --all build passed having checked nothing."""
+
+    def test_both_raise(self):
+        from scripts.common import list_registered_platforms
+
+        with tempfile.TemporaryDirectory(dir=TMP_ROOT) as tmp:
+            with self.assertRaises(FileNotFoundError):
+                list_registered_platforms(tmp)
+            Path(tmp, "_registry.yml").write_text(
+                "platforms:\n  rocknix:\n    config: rocknix.yml\n", encoding="utf-8"
+            )
+            with self.assertRaises(FileNotFoundError) as caught:
+                list_registered_platforms(tmp)
+            self.assertIn("rocknix", str(caught.exception))
+
+
 if __name__ == "__main__":
     unittest.main()