Pass 3D wrench buffer to LINK_WRENCH binding

The OVPhysX wheel's ``LINK_WRENCH`` binding expects a 3D
``(num_instances, num_bodies, 9)`` tensor (force ⊕ torque ⊕ position),
but ``compute()`` was passing the 2D ``(N*B, 9)`` flat reshape view, so
the wheel rejected with ``write_tensor_binding: expected 3D tensor, got
2D``.  Pass the 3D buffer directly and drop the now-unused flat alias.

Author: AntoineRichard

source/isaaclab_ovphysx/isaaclab_ovphysx/assets/articulation/articulation.py

@@ -226,7 +226,7 @@ def write_data_to_sim(self) -> None:
             )
             binding = self._get_binding(TT.LINK_WRENCH)
             if binding is not None:
-                binding.write(self._wrench_buf_flat)
+                binding.write(self._wrench_buf)
             inst.reset()
 
         # 2. Actuator model.
@@ -695,17 +695,10 @@ def _create_buffers(self) -> None:
         self._ALL_TRUE_FIXED_TENDON_MASK = wp.array(np.ones(FT, dtype=bool), dtype=wp.bool, device=device)
         self._ALL_TRUE_SPATIAL_TENDON_MASK = wp.array(np.ones(ST, dtype=bool), dtype=wp.bool, device=device)
 
-        # Wrench buffer + flat view (multi-body generalization).
-        # The kernel writes into the (N, B, 9) view; the binding consumes the (N*B, 9)
-        # view -- both alias the same allocation, so we cache the flat reshape once.
+        # Wrench buffer (force, torque, position) per body, written by the
+        # ``_body_wrench_to_world`` kernel and consumed by the
+        # ``LINK_WRENCH`` binding which expects the 3D ``(N, B, 9)`` shape.
         self._wrench_buf = wp.zeros((N, B, 9), dtype=wp.float32, device=device)
-        self._wrench_buf_flat = wp.array(
-            ptr=self._wrench_buf.ptr,
-            shape=(N * B, 9),
-            dtype=wp.float32,
-            device=device,
-            copy=False,
-        )
 
         # Wrench composers.
         self._instantaneous_wrench_composer = WrenchComposer(self)