Refactors the doc on Schema for Lab 3.0, and adds MuJoCo gravcomp (#5276)

# Description

Adds Newton-native and MuJoCo-specific schema cfg classes to
`isaaclab_newton.sim.schemas`,
following the base/subclass framework from #5275. All new cfgs use the
per-declaring-class
MRO routing in `_apply_namespaced_schemas` — no backend-specific
branching in any writer.

Depends on #5275.

## New cfgs

### MuJoCo (Newton MuJoCo kernel, `mjc:*` namespace)

| Class | Field | USD attribute | Applied schema |
|---|---|---|---|
| `MujocoRigidBodyPropertiesCfg` | `gravcomp` | `mjc:gravcomp` | None
(raw attr) |
| `MujocoJointDrivePropertiesCfg` | `actuatorgravcomp` |
`mjc:actuatorgravcomp` | `MjcJointAPI` |

Body-level `gravcomp` must be set for joint-level `actuatorgravcomp` to
have any effect.
The spawner auto-enables `MujocoRigidBodyPropertiesCfg(gravcomp=1.0)`
when joint-level
actuator gravcomp is requested without body-level gravcomp.

### Newton-native (`newton:*` namespace)

| Class | Fields | USD attributes | Applied schema |
|---|---|---|---|
| `NewtonCollisionPropertiesCfg` | `contact_margin`, `contact_gap` |
`newton:contactMargin`, `newton:contactGap` | `NewtonCollisionAPI` |
| `NewtonMeshCollisionPropertiesCfg` | `max_hull_vertices` |
`newton:maxHullVertices` | `NewtonMeshCollisionAPI` |
| `NewtonMaterialPropertiesCfg` | `torsional_friction`,
`rolling_friction` | `newton:torsionalFriction`,
`newton:rollingFriction` | `NewtonMaterialAPI` |
| `NewtonArticulationRootPropertiesCfg` | `self_collision_enabled` |
`newton:selfCollisionEnabled` | `NewtonArticulationRootAPI` |

## Design constraints

Same single-cfg-per-spawner-slot rule as #5275. Newton cfgs subclass the
same base classes
as PhysX cfgs; each declares `_usd_namespace`/`_usd_applied_schema`
(ClassVar) and fields
that auto-camelCase to their USD attr names. Per-declaring-class MRO
routing handles mixed
PhysX+Newton cfg hierarchies correctly.

## Field renames (with deprecation aliases through 5.0)

| Old | New | Reason |
|---|---|---|
| `gravity_compensation_scale` | `gravcomp` | Single word identity:
`gravcomp` → `mjc:gravcomp` |
| `gravity_compensation` | `actuatorgravcomp` | Single word identity:
`actuatorgravcomp` → `mjc:actuatorgravcomp` |

## Type of change

- New feature (non-breaking)

Forwarding shims on `isaaclab.sim.schemas` keep existing imports
working.
Deprecation aliases keep old field names working through 5.0.

## Test plan

- [x] MuJoCo tests: `mjc:gravcomp` / `mjc:actuatorgravcomp` written when
set, not written when None
- [x] Newton collision, material, articulation-root: attrs written,
schemas applied only when non-None
- [x] Deprecation alias tests for renamed fields
- [x] `test_schemas.py` 46/46 pass — no regressions
- [x] Pre-commit clean

## Supersedes

Together with #5275, supersedes #4847 and #5203.

---------

Co-authored-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Antoine RICHARD <antoiner@nvidia.com>

Author: 3 people

docs/source/api/index.rst

@@ -161,6 +161,7 @@ The following modules are available in the ``isaaclab_newton`` extension:
    renderers
    scene_data_providers
    sensors
+   sim.schemas
 
 .. toctree::
    :hidden:
@@ -171,6 +172,7 @@ The following modules are available in the ``isaaclab_newton`` extension:
    lab_newton/isaaclab_newton.renderers
    lab_newton/isaaclab_newton.scene_data_providers
    lab_newton/isaaclab_newton.sensors
+   lab_newton/isaaclab_newton.sim.schemas
 
 isaaclab_ov extension
 ---------------------

docs/source/api/lab/isaaclab.sim.schemas.rst

@@ -1,18 +1,31 @@
-isaaclab.sim.schemas
+isaaclab.sim.schemas
 ====================
 
 .. automodule:: isaaclab.sim.schemas
 
-  .. rubric:: Classes
+  .. rubric:: Solver-common base classes
+
+  These base classes carry the universal-physics fields that every backend honors.
+  They live in core ``isaaclab`` and have no backend dependency. For backend-specific
+  knobs, use the matching subclass in :mod:`isaaclab_physx.sim.schemas` or
+  :mod:`isaaclab_newton.sim.schemas`. See :doc:`/source/overview/core-concepts/schema_cfgs`
+  for the full design.
 
   .. autosummary::
 
-    ArticulationRootPropertiesCfg
-    RigidBodyPropertiesCfg
-    CollisionPropertiesCfg
+    ArticulationRootBaseCfg
+    RigidBodyBaseCfg
+    CollisionBaseCfg
+    JointDriveBaseCfg
+    MeshCollisionBaseCfg
     MassPropertiesCfg
-    JointDrivePropertiesCfg
-    FixedTendonPropertiesCfg
+
+  .. rubric:: Mesh collision approximations (USD-only, no PhysX schema)
+
+  .. autosummary::
+
+    BoundingCubePropertiesCfg
+    BoundingSpherePropertiesCfg
 
   .. rubric:: Functions
 
@@ -28,39 +41,60 @@
     define_mass_properties
     modify_mass_properties
     modify_joint_drive_properties
+    define_mesh_collision_properties
+    modify_mesh_collision_properties
     modify_fixed_tendon_properties
+    modify_spatial_tendon_properties
+
+.. currentmodule:: isaaclab.sim.schemas
 
 Articulation Root
 -----------------
 
-.. autoclass:: ArticulationRootPropertiesCfg
+.. autoclass:: ArticulationRootBaseCfg
     :members:
     :exclude-members: __init__
 
 .. autofunction:: define_articulation_root_properties
 .. autofunction:: modify_articulation_root_properties
 
+For PhysX-specific articulation properties (self-collisions, TGS solver iterations,
+sleep/stabilization thresholds), see
+:class:`~isaaclab_physx.sim.schemas.PhysxArticulationRootPropertiesCfg`. For
+Newton-native self-collisions, see
+:class:`~isaaclab_newton.sim.schemas.NewtonArticulationRootPropertiesCfg`.
+
 Rigid Body
 ----------
 
-.. autoclass:: RigidBodyPropertiesCfg
+.. autoclass:: RigidBodyBaseCfg
     :members:
     :exclude-members: __init__
 
 .. autofunction:: define_rigid_body_properties
 .. autofunction:: modify_rigid_body_properties
 .. autofunction:: activate_contact_sensors
 
+For PhysX-specific rigid body properties (damping, max velocities, solver iterations,
+sleep/stabilization), see :class:`~isaaclab_physx.sim.schemas.PhysxRigidBodyPropertiesCfg`.
+For MuJoCo-specific gravity compensation, see
+:class:`~isaaclab_newton.sim.schemas.MujocoRigidBodyPropertiesCfg`.
+
 Collision
 ---------
 
-.. autoclass:: CollisionPropertiesCfg
+.. autoclass:: CollisionBaseCfg
     :members:
     :exclude-members: __init__
 
 .. autofunction:: define_collision_properties
 .. autofunction:: modify_collision_properties
 
+For PhysX torsional patch friction, see
+:class:`~isaaclab_physx.sim.schemas.PhysxCollisionPropertiesCfg`. For Newton-native
+contact margin/gap, see
+:class:`~isaaclab_newton.sim.schemas.NewtonCollisionPropertiesCfg`.
+
 Mass
 ----
 
@@ -74,20 +108,52 @@ Mass
 Joint Drive
 -----------
 
-.. autoclass:: JointDrivePropertiesCfg
+.. autoclass:: JointDriveBaseCfg
     :members:
     :exclude-members: __init__
 
 .. autofunction:: modify_joint_drive_properties
 
-Fixed Tendon
-------------
+For PhysX-specific drive properties, see
+:class:`~isaaclab_physx.sim.schemas.PhysxJointDrivePropertiesCfg`. For MuJoCo
+actuator gravity compensation, see
+:class:`~isaaclab_newton.sim.schemas.MujocoJointDrivePropertiesCfg`.
+
+Mesh Collision
+--------------
 
-.. autoclass:: FixedTendonPropertiesCfg
+.. autoclass:: MeshCollisionBaseCfg
     :members:
     :exclude-members: __init__
 
+.. autoclass:: BoundingCubePropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: BoundingSpherePropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autofunction:: define_mesh_collision_properties
+.. autofunction:: modify_mesh_collision_properties
+
+For PhysX cooking schemas (convex hull / decomposition / triangle mesh / SDF),
+see the ``Physx*PropertiesCfg`` family in :mod:`isaaclab_physx.sim.schemas`.
+For Newton hull-vertex limit, see
+:class:`~isaaclab_newton.sim.schemas.NewtonMeshCollisionPropertiesCfg`.
+
+Tendon
+------
+
 .. autofunction:: modify_fixed_tendon_properties
+.. autofunction:: modify_spatial_tendon_properties
+
+Tendon cfg classes are PhysX-only and live in
+:mod:`isaaclab_physx.sim.schemas`
+(:class:`~isaaclab_physx.sim.schemas.PhysxFixedTendonPropertiesCfg`,
+:class:`~isaaclab_physx.sim.schemas.PhysxSpatialTendonPropertiesCfg`).
 
 Deformable Body
 ---------------

docs/source/api/lab_newton/isaaclab_newton.sim.schemas.rst

@@ -0,0 +1,88 @@
+isaaclab_newton.sim.schemas
+===========================
+
+.. automodule:: isaaclab_newton.sim.schemas
+
+  Newton-targeted schema configuration classes. Each cfg below extends a
+  solver-common base in :mod:`isaaclab.sim.schemas` with Newton-namespaced
+  attributes (``newton:*``) or solver-specific attributes (``mjc:*`` for
+  Newton's MuJoCo solver). MuJoCo cfgs subclass their Newton counterpart
+  because MuJoCo is one of Newton's solver options.
+
+  See :doc:`/source/overview/core-concepts/schema_cfgs` for the design and
+  when to use each class.
+
+  .. rubric:: Newton-targeted (family roots)
+
+  .. autosummary::
+
+    NewtonRigidBodyPropertiesCfg
+    NewtonJointDrivePropertiesCfg
+    NewtonCollisionPropertiesCfg
+    NewtonMeshCollisionPropertiesCfg
+    NewtonMaterialPropertiesCfg
+    NewtonArticulationRootPropertiesCfg
+
+  .. rubric:: MuJoCo-solver-specific
+
+  .. autosummary::
+
+    MujocoRigidBodyPropertiesCfg
+    MujocoJointDrivePropertiesCfg
+
+.. currentmodule:: isaaclab_newton.sim.schemas
+
+Rigid Body
+----------
+
+.. autoclass:: NewtonRigidBodyPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: MujocoRigidBodyPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Joint Drive
+-----------
+
+.. autoclass:: NewtonJointDrivePropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: MujocoJointDrivePropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Collision
+---------
+
+.. autoclass:: NewtonCollisionPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: NewtonMeshCollisionPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Material
+--------
+
+.. autoclass:: NewtonMaterialPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Articulation Root
+-----------------
+
+.. autoclass:: NewtonArticulationRootPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__

docs/source/api/lab_physx/isaaclab_physx.sim.schemas.rst

@@ -3,7 +3,49 @@ isaaclab_physx.sim.schemas
 
 .. automodule:: isaaclab_physx.sim.schemas
 
-  .. rubric:: Classes
+  PhysX-specific schema configuration classes. Each cfg below extends a
+  solver-common base in :mod:`isaaclab.sim.schemas` with PhysX-namespaced
+  attributes (``physx*:*``) and applies the corresponding ``Physx*API``
+  applied schema. See :doc:`/source/overview/core-concepts/schema_cfgs`
+  for the design.
+
+  .. rubric:: Rigid body and joint drive
+
+  .. autosummary::
+
+    PhysxRigidBodyPropertiesCfg
+    PhysxJointDrivePropertiesCfg
+
+  .. rubric:: Collision
+
+  .. autosummary::
+
+    PhysxCollisionPropertiesCfg
+
+  .. rubric:: Articulation root
+
+  .. autosummary::
+
+    PhysxArticulationRootPropertiesCfg
+
+  .. rubric:: Mesh collision (PhysX cooking)
+
+  .. autosummary::
+
+    PhysxConvexHullPropertiesCfg
+    PhysxConvexDecompositionPropertiesCfg
+    PhysxTriangleMeshPropertiesCfg
+    PhysxTriangleMeshSimplificationPropertiesCfg
+    PhysxSDFMeshPropertiesCfg
+
+  .. rubric:: Tendon
+
+  .. autosummary::
+
+    PhysxFixedTendonPropertiesCfg
+    PhysxSpatialTendonPropertiesCfg
+
+  .. rubric:: Deformable body
 
   .. autosummary::
 
@@ -18,6 +60,79 @@ isaaclab_physx.sim.schemas
 
 .. currentmodule:: isaaclab_physx.sim.schemas
 
+Rigid Body
+----------
+
+.. autoclass:: PhysxRigidBodyPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Joint Drive
+-----------
+
+.. autoclass:: PhysxJointDrivePropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Collision
+---------
+
+.. autoclass:: PhysxCollisionPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Articulation Root
+-----------------
+
+.. autoclass:: PhysxArticulationRootPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Mesh Collision (PhysX cooking)
+-------------------------------
+
+.. autoclass:: PhysxConvexHullPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: PhysxConvexDecompositionPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: PhysxTriangleMeshPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: PhysxTriangleMeshSimplificationPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: PhysxSDFMeshPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+Tendon
+------
+
+.. autoclass:: PhysxFixedTendonPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
+.. autoclass:: PhysxSpatialTendonPropertiesCfg
+    :members:
+    :show-inheritance:
+    :exclude-members: __init__
+
 Deformable Body
 ---------------