Test fixture: set _step_count for a complete ready state

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/validation/multigrid/test_block_stepper.py

@@ -113,6 +113,7 @@ class CpuContracts(unittest.TestCase):
         backend.ctx = Mock(activate=nullcontext)
         backend._lock = RLock()
         backend._status = "ready"
+        backend._step_count = 0
         backend._stream = Mock()
         backend._module = Mock()
         backend._copy = backend._step = Mock()