Start in cold manual state with rods inserted

src/reactor_sim/reactor.py

@@ -76,6 +76,16 @@ class Reactor:
             fission_product_inventory={},
             emitted_particles={},
         )
+        # Default to a cold, safe configuration: rods fully inserted, manual control, pumps/turbines off.
+        self.control.manual_control = True
+        self.control.rod_fraction = 0.95
+        self.primary_pump_active = False
+        self.secondary_pump_active = False
+        self.turbine_unit_active = [False] * len(self.turbines)
+        self.turbine_active = any(self.turbine_unit_active)
+        if self.consumer:
+            self.consumer.set_online(False)
+
         primary = CoolantLoopState(
             temperature_in=ambient,
             temperature_out=ambient,