Support bounded machine instruction step counts in MCP

tests/sdbg/test_server.py

@@ -111,13 +111,16 @@ class StepBridge:
     def __init__(self, owner):
         self.owner = owner
         self.calls = []
+        self.step_counts = []
 
     def close(self): pass
 
     def request(self, command, **arguments):
         self.calls.append(command)
         if command in ('step', 'step_over', 'step_out'):
-            self.owner.index = min(self.owner.index + 1,
+            count = arguments.get('count', 1) if command == 'step' else 1
+            self.step_counts.append(count)
+            self.owner.index = min(self.owner.index + count,
                                    len(self.owner.locations) - 1)
             return {'accepted': True}
         if command == 'snapshot':
@@ -482,6 +485,21 @@ class ServerTests(unittest.TestCase):
         finally:
             controller.close()
 
+    def test_instruction_step_count_is_bounded_and_forwarded(self):
+        session = StepSession()
+        controller = SessionController(session)
+        try:
+            with self.assertRaisesRegex(SessionError, '1..64'):
+                controller.call('step', {'count': 0, 'owner': 'mcp:test'})
+            for bad in (65, 1.5, True):
+                with self.assertRaisesRegex(SessionError, '1..64'):
+                    controller.call('step', {'count': bad, 'owner': 'mcp:test'})
+            result = controller.call('step', {'count': 2, 'owner': 'mcp:test'})
+            self.assertEqual(result['sources'][0]['line'], 4)
+            self.assertEqual(session.bridge.step_counts, [2])
+        finally:
+            controller.close()
+
     def test_source_step_preserves_user_breakpoint_on_same_line(self):
         session = StepSession()
         controller = SessionController(session)