Skip OVPhysX contact-sensor tests when the wheel is unavailable

The CI ``isaaclab_ov*`` filter collects the OVPhysX contact-sensor
tests in Docker images that do not yet bundle the ``ovphysx`` wheel,
causing ``ModuleNotFoundError`` at collection time and a red required
check.

Match the precedent set by
``source/isaaclab_ovphysx/test/assets/test_articulation_helpers.py``
and ``test_rigid_object_helpers.py``: move the existing
``pytest.importorskip("ovphysx.types", ...)`` guard above the
``from isaaclab_ovphysx ...`` imports so the file is skipped before
the missing wheel can break collection.

Also add the missing ``isaaclab_tasks`` changelog fragment for the
``AnymalD Flat`` and ``LocomotionVelocityRoughEnvCfg`` ovphysx-preset
wiring that PR 5422 ships.

Author: AntoineRichard

source/isaaclab_ovphysx/test/sensors/test_contact_sensor.py

@@ -44,26 +44,25 @@
 import torch
 import warp as wp
 from flaky import flaky
-from isaaclab_ovphysx.assets import RigidObject
-from isaaclab_ovphysx.physics import OvPhysxCfg
-from isaaclab_ovphysx.sensors import ContactSensor
-
-import isaaclab.sim as sim_utils
-from isaaclab.assets import RigidObjectCfg
-from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
-from isaaclab.sim import SimulationCfg, SimulationContext, build_simulation_context
-from isaaclab.sim.utils.stage import get_current_stage
-from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg
-from isaaclab.utils.configclass import configclass
 
-wp.init()
-
-# The CI isaaclab_ov* pattern may collect these tests in environments where the
-# ovphysx wheel is not installed.  Skip gracefully so other pipelines are not
-# blocked by a missing dependency.
+# The CI isaaclab_ov* pattern unintentionally collects isaaclab_ovphysx tests,
+# but the ovphysx wheel is not installed in that environment. Skip gracefully
+# so the isaaclab_ov CI pipeline is not blocked by an unrelated dependency.
 pytest.importorskip("ovphysx.types", reason="ovphysx wheel not installed")
 
-from isaaclab_ovphysx.sensors import ContactSensorCfg  # noqa: E402
+from isaaclab_ovphysx.assets import RigidObject  # noqa: E402
+from isaaclab_ovphysx.physics import OvPhysxCfg  # noqa: E402
+from isaaclab_ovphysx.sensors import ContactSensor, ContactSensorCfg  # noqa: E402
+
+import isaaclab.sim as sim_utils  # noqa: E402
+from isaaclab.assets import RigidObjectCfg  # noqa: E402
+from isaaclab.scene import InteractiveScene, InteractiveSceneCfg  # noqa: E402
+from isaaclab.sim import SimulationCfg, SimulationContext, build_simulation_context  # noqa: E402
+from isaaclab.sim.utils.stage import get_current_stage  # noqa: E402
+from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg  # noqa: E402
+from isaaclab.utils.configclass import configclass  # noqa: E402
+
+wp.init()
 
 # ---------------------------------------------------------------------------
 # Device-lock autouse fixture

source/isaaclab_tasks/changelog.d/antoiner-feat-ovphysx_contactsensor.rst

@@ -0,0 +1,10 @@
+Added
+^^^^^
+
+* Added ``ovphysx`` preset to ``isaaclab_tasks.manager_based.locomotion.velocity``
+  for use under the OVPhysX backend. ``AnymalDFlatPhysicsCfg`` now exposes
+  an ``ovphysx`` member, and the shared ``LocomotionVelocityRoughEnvCfg``
+  injects the OVPhysX :class:`~isaaclab_ovphysx.sensors.ContactSensorCfg`
+  alongside the existing PhysX and Newton entries so the velocity task
+  selects the right contact sensor backend when run with
+  ``presets=ovphysx``.