fix(mcp): use module-level time so test patches do not race background sleepers

tools/mcp_tool.py

@@ -3518,7 +3518,6 @@ def _kill_orphaned_mcp_children(include_active: bool = False) -> None:
     sessions can still be in flight.
     """
     import signal as _signal
-    import time as _time
 
     with _lock:
         pids: Dict[int, str] = {}
@@ -3543,7 +3542,7 @@ def _kill_orphaned_mcp_children(include_active: bool = False) -> None:
             pass
 
     # Phase 2: Wait for graceful exit
-    _time.sleep(2)
+    time.sleep(2)
 
     # Phase 3: SIGKILL any survivors
     _sigkill = getattr(_signal, "SIGKILL", _signal.SIGTERM)