fix(newton): support newton 1.5/1.6 (removed attributes, target layout, tiled camera)

CHANGELOG.md

@@ -39,6 +39,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - IsaacGym and PyBullet reported `joint_pos_target` in native DoF order while `joint_pos` is in sorted-name order; both now use `get_joint_names(sort=True)` (completes #12).
 - `ParallelSimWrapper`: a worker that died during handler construction or `launch` surfaced as a bare `EOFError`/`ConnectionResetError` from the handshake and left the other workers running; the handshake now raises the worker's own traceback, `close()` tolerates dead workers, and a failed constructor tears the pool down.
 - `hf_util.check_and_download_single`: a `roboverse_data/...` path evaluated from a working directory that is not the parent of `ROBOVERSE_DATA_DIR` was reported as a path-traversal attempt; the error now names the CWD / `ROBOVERSE_DATA_DIR` mismatch and where the asset already is. `test_check_and_download_single_falls_back_to_private_roboverse_data` no longer depends on the caller's `ROBOVERSE_DATA_DIR`.
+- Newton backend works again on the pinned newton (1.5/1.6): `joint_target_pos`/`joint_target_vel` and `num_worlds` are forwarded to their new names, position targets use `joint_target_q_start` (on newton >= 1.5 they follow the `joint_q` layout, so envs after a free-floating object were driven to the wrong joints), the tiled camera uses the 1.4+ `RenderConfig`/`utils`/`update` API with an untextured fallback, and `CameraState.depth` is `(N, H, W)`.
 - MuJoCo: `<size memory="512M">` is reserved by default; humanoid + mesh scenes no longer die with
   `mj_stackAlloc: out of memory` (get_started/10_mount_camera.py).
 - `hf_util`: a symlinked `roboverse_data` is no longer refused as path traversal; concurrent

metasim/sim/newton/_newton_compat.py

@@ -18,6 +18,9 @@
 - Model attribute aliases body_key / joint_key / shape_key -> *_label
 - add_mjcf(builder, path, **kw): ModelBuilder.add_mjcf method removed
   in 1.2 but parse_mjcf in newton._src.utils.import_mjcf still works
+- Model/Control joint_target_pos / joint_target_vel -> joint_target_q /
+  joint_target_qd (removed in 1.5; the new names are forwarded read/write)
+- Model.num_worlds -> Model.world_count (renamed in 1.6)
 
 Backward-compat guarantee:
 - Anything that worked on newton < 1.2 still works.
@@ -123,6 +126,71 @@ def _install_model_attr_aliases():
 _install_model_attr_aliases()
 
 
+def _install_removed_attr_aliases():
+    """Route attributes newton 1.5 removed back to their replacements.
+
+    newton 1.5 renamed ``joint_target_pos`` / ``joint_target_vel`` to ``joint_target_q`` /
+    ``joint_target_qd`` on both ``Model`` and ``Control`` and shadows the old names with a
+    ``RemovedAttribute`` descriptor that raises on read *and* write. The handler reads and
+    assigns both, so install read/write properties that forward to the new instance attributes.
+    Older newton (real attributes, no descriptor) is left untouched.
+    """
+    try:
+        import newton
+    except ImportError:
+        return
+    renames = [("joint_target_pos", "joint_target_q"), ("joint_target_vel", "joint_target_qd")]
+    for cls_name in ("Model", "Control"):
+        cls = getattr(newton, cls_name, None)
+        if cls is None:
+            continue
+        for old, new in renames:
+            current = cls.__dict__.get(old)
+            if current is None or type(current).__name__ != "RemovedAttribute":
+                continue
+
+            def _get(self, _n=new):
+                return getattr(self, _n)
+
+            def _set(self, value, _n=new):
+                setattr(self, _n, value)
+
+            setattr(cls, old, property(_get, _set))
+
+
+_install_removed_attr_aliases()
+
+
+def _install_renamed_attr_aliases():
+    """Forward attribute names newton renamed *without* leaving a descriptor behind.
+
+    ``Model.num_worlds`` became ``Model.world_count`` in newton 1.6 and simply disappeared. The
+    alias reads the instance attribute when an older newton still sets it and falls back to the
+    new name otherwise, so both spellings work on every version.
+    """
+    try:
+        import newton
+    except ImportError:
+        return
+    for cls_name, old, new in [("Model", "num_worlds", "world_count")]:
+        cls = getattr(newton, cls_name, None)
+        if cls is None or old in cls.__dict__:
+            continue
+
+        def _get(self, _old=old, _new=new):
+            if _old in self.__dict__:
+                return self.__dict__[_old]
+            return getattr(self, _new)
+
+        def _set(self, value, _old=old):
+            self.__dict__[_old] = value
+
+        setattr(cls, old, property(_get, _set))
+
+
+_install_renamed_attr_aliases()
+
+
 def add_mjcf(builder, mjcf_path: str, **kwargs):
     """Add an MJCF file to ``ModelBuilder``, version-portable.