✨ add rotary cartpole env

src/core/env.py

@@ -57,3 +57,10 @@ class BaseEnv(abc.ABC, Generic[T]):
 
     def compute_truncations(self, step_counts: torch.Tensor) -> torch.Tensor:
         return step_counts >= self.config.max_steps
+
+    def get_default_qpos(self, nq: int) -> list[float] | None:
+        """Return the default joint positions for reset.
+        Override in subclass if the URDF zero pose doesn't match
+        the desired initial state (e.g. pendulum hanging down).
+        Returns None to use the URDF default (all zeros)."""
+        return None