fix: adapted simulation config

configs/simulation/default.yaml

@@ -8,4 +8,9 @@ model_path: null
 model_type: "random"
 
 # Execution backend (MJX or BRAX)
-backend: "MJX"
+backend: "MJC"
+
+# Script behavior
+headless: false
+# In headless mode this is required; in viewer mode null means "infinite".
+max_steps: null

src/brittle_star_project/configs/config_simulation.py

@@ -1,5 +1,6 @@
 from dataclasses import dataclass
 from typing import Optional
+
 from brittle_star_project.environment.env_types import Backend
 
 
@@ -9,4 +10,9 @@ class SimulationSettings:
 
     model_path: Optional[str] = None
     model_type: str = "random"
-    backend: Backend = Backend.MJX
+    backend: Backend = Backend.MJC
+
+    # Script behavior
+    headless: bool = False
+    # If None, viewer mode runs until window closed or target reached.
+    max_steps: Optional[int] = None