fix: create fallback state file with owner-only 0600 permissions

app/state_store.py

@@ -148,7 +148,11 @@ class AtomicJsonStore:
             raise
 
     def _direct_write(self, payload: dict[str, Any]) -> None:
-        with open(self.path, "w", encoding="utf-8") as f:
+        # Create with 0o600 so the fallback keeps the owner-only permissions the
+        # atomic path gets from mkstemp; state files can contain URLs and
+        # per-download option overrides that must not leak on shared mounts.
+        fd = os.open(self.path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+        with os.fdopen(fd, "w", encoding="utf-8") as f:
             self._write_payload(payload, f)
             f.flush()
             self._best_effort_fsync(f.fileno())

app/tests/test_state_store.py

@@ -36,6 +36,8 @@ class StateStoreTests(unittest.TestCase):
 
             self.assertTrue(os.path.exists(path))
             self.assertTrue(any(path in message for message in logs.output))
+            # Fallback keeps owner-only permissions, matching the atomic path.
+            self.assertEqual(os.stat(path).st_mode & 0o777, 0o600)
             payload = store.load()
             self.assertEqual(payload["items"], [{"key": "a"}])
 
@@ -64,7 +66,10 @@ class StateStoreTests(unittest.TestCase):
                 "state_store.tempfile.mkstemp",
                 side_effect=PermissionError(1, "Operation not permitted"),
             ):
-                with patch("builtins.open", side_effect=PermissionError(13, "Permission denied")):
+                with patch(
+                    "state_store.os.open",
+                    side_effect=PermissionError(13, "Permission denied"),
+                ):
                     with self.assertRaises(PermissionError) as ctx:
                         store.save({"items": [{"key": "a"}]})