Simulator: metadrive is the default (#30133)

only docs and default

tools/sim/README.md

@@ -57,7 +57,7 @@ Start bridge processes located in tools/sim:
 
 ## Carla
 
-openpilot doesn't have any extreme hardware requirements, however CARLA requires an NVIDIA graphics card and is very resource-intensive and may not run smoothly on your system.
+CARLA is also partially supported, though the performance is not great. openpilot doesn't have any extreme hardware requirements, however CARLA requires an NVIDIA graphics card and is very resource-intensive and may not run smoothly on your system.
 For this case, we have the simulator in low quality by default.
 
 You can also check out the [CARLA python documentation](https://carla.readthedocs.io/en/latest/python_api/) to find more parameters to tune that might increase performance on your system.

tools/sim/run_bridge.py

@@ -15,7 +15,7 @@ def parse_args(add_args=None):
   parser.add_argument('--joystick', action='store_true')
   parser.add_argument('--high_quality', action='store_true')
   parser.add_argument('--dual_camera', action='store_true')
-  parser.add_argument('--simulator', dest='simulator', type=str, default='carla')
+  parser.add_argument('--simulator', dest='simulator', type=str, default='metadrive')
 
   # Carla specific
   parser.add_argument('--town', type=str, default='Town04_Opt')