Align OVPhysX ContactSensor parity with PhysX/Newton

Three small parity fixes that came out of a code review against the
PhysX/Newton implementations:

* Rename ``update_net_forces_kernel`` to
  ``update_net_forces_ovphysx_kernel``. PhysX ships a kernel of the same
  name with a different signature (env-major vs sensor-major index
  order); the explicit suffix prevents a confusing compile error if
  someone cross-imports.
* ``ContactSensor.body_names`` now returns ``list[str]`` (never ``None``)
  and raises a clear ``RuntimeError`` if accessed before initialization,
  matching the PhysX contract.
* Add ``_set_debug_vis_impl`` and a no-op ``_debug_vis_callback`` to the
  OVPhysX ContactSensor. The kitless OVPhysX flow has no Kit renderer,
  so the implementations log a one-shot warning and otherwise no-op,
  but the hooks are wired so ``cfg.debug_vis=True`` surfaces an
  explicit message instead of silently doing nothing.

Author: AntoineRichard

source/isaaclab_ovphysx/isaaclab_ovphysx/sensors/contact_sensor/contact_sensor.py

@@ -9,6 +9,7 @@
 from __future__ import annotations
 
 import contextlib
+import logging
 import re
 from collections.abc import Sequence
 from typing import TYPE_CHECKING, Any
@@ -28,12 +29,14 @@
     reset_contact_sensor_kernel,
     split_flat_pose_to_pos_quat,
     unpack_contact_buffer_data,  # noqa: F401  -- reserved for v2 contact-points support
-    update_net_forces_kernel,
+    update_net_forces_ovphysx_kernel,
 )
 
 if TYPE_CHECKING:
     from .contact_sensor_cfg import ContactSensorCfg
 
+logger = logging.getLogger(__name__)
+
 
 class ContactSensor(BaseContactSensor):
     """An ovphysx contact reporting sensor.
@@ -131,9 +134,19 @@ def num_sensors(self) -> int:
         return self._num_sensors
 
     @property
-    def body_names(self) -> list[str] | None:
+    def body_names(self) -> list[str]:
+        """The leaf-prim names of the sensor bodies.
+
+        Raises:
+            RuntimeError: If accessed before the sensor has been initialized
+                (matches the eager non-``None`` contract PhysX provides).
+        """
         if not self._body_names:
-            return None
+            raise RuntimeError(
+                "OvPhysxContactSensor.body_names accessed before initialization. "
+                "Step the simulation once (or wait for PhysicsEvent.PHYSICS_READY) so the "
+                "sensor can discover its bodies."
+            )
         return list(self._body_names)
 
     @property
@@ -330,7 +343,7 @@ def _update_buffers_impl(self, env_mask: wp.array | None = None) -> None:
             force_matrix_flat = None
 
         wp.launch(
-            update_net_forces_kernel,
+            update_net_forces_ovphysx_kernel,
             dim=(self._num_envs, self._num_sensors),
             inputs=[
                 net_forces_flat,
@@ -453,6 +466,35 @@ def compute_first_air(self, dt: float, abs_tol: float = 1.0e-8) -> ProxyArray:
         )
         return self._data._first_transition_ta
 
+    """
+    Debug visualization
+    """
+
+    def _set_debug_vis_impl(self, debug_vis: bool) -> None:
+        """Toggle contact-marker visibility.
+
+        The kitless OVPhysX flow has no Kit-based renderer, so visualization
+        markers are effectively invisible. The hook is still wired so that
+        callers setting ``cfg.debug_vis=True`` get an explicit warning rather
+        than silent no-op behaviour.
+        """
+        if debug_vis and not getattr(self, "_warned_debug_vis_unavailable", False):
+            logger.warning(
+                "OVPhysX ContactSensor: debug visualization markers are not rendered under the "
+                "kitless OVPhysX flow (no Kit renderer present). The hook runs but marker "
+                "geometry will not appear."
+            )
+            self._warned_debug_vis_unavailable = True
+
+    def _debug_vis_callback(self, event) -> None:
+        """Per-frame visualization update.
+
+        Under kitless OVPhysX this is a no-op -- there is no renderer driving
+        the per-frame marker positions. The method exists so the base
+        sensor's debug-vis lifecycle hooks have a callable target.
+        """
+        return
+
     """
     Internal simulation callbacks.
     """

source/isaaclab_ovphysx/isaaclab_ovphysx/sensors/contact_sensor/kernels.py

@@ -187,7 +187,7 @@ def compute_first_transition_kernel(
 
 
 @wp.kernel
-def update_net_forces_kernel(
+def update_net_forces_ovphysx_kernel(
     # in
     net_forces_flat: wp.array(dtype=wp.vec3f),
     net_forces_matrix_flat: wp.array2d(dtype=wp.vec3f),