WIP: G1 rough-terrain fixes — remove fingers from action space + Newton armature/damping presets

Reduces action_rate_l2 penalty from -0.6 to -0.25 by restricting the
14 finger joints from the action vector; locomotion-relevant joints only
(hips, knees, ankles, shoulders, elbows, torso).

Adds Newton-only armature (0.03) and damping (20.0) presets on the legs
actuator to stabilize G1 under the MJWarp solver where the USD baseline
values (armature=0.01, damping=5.0) produce excessive oscillation.

Measured results (1500 iter, 4096 envs, last30 avg reward):
  - G1 PhysX baseline:                          +11.68
  - G1 PhysX (fingers-out-of-action):           +20.54  (beats H1 PhysX +18.15)
  - G1 Newton baseline:                         -2.33
  - G1 Newton (fingers-out-of-action):          +5.35
  - G1 Newton (fingers + armature + damping):   +9.61   (47% of PhysX)

Newton still lags PhysX on G1; residual gap is physics-level and out
of scope for this PR. Marking WIP pending further tuning or upstream
Newton improvements.

Author: hujc7

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/g1/rough_env_cfg.py

@@ -13,6 +13,7 @@
     LocomotionVelocityRoughEnvCfg,
     RewardsCfg,
 )
+from isaaclab_tasks.utils import preset
 
 ##
 # Pre-defined configs
@@ -144,6 +145,22 @@ def __post_init__(self):
         # terminations
         self.terminations.base_contact.params["sensor_cfg"].body_names = "torso_link"
 
+        # G1 H1: remove finger joints from the action space. 14 finger joints contribute
+        # to action_rate_l2 penalty (G1 hits -0.6 at 1500 iter vs H1's -0.2 — 3x
+        # penalty from extra dims). Restrict actions to locomotion-relevant joints.
+        self.actions.joint_pos.joint_names = [
+            ".*_hip_.*", ".*_knee_joint", ".*_ankle_.*", ".*_shoulder_.*", ".*_elbow_.*",
+            "torso_joint",
+        ]
+
+        # G1 Newton armature bump (Go2-pattern). Baseline G1 Newton lagged PhysX even
+        # after the finger-space fix (5.35 vs 20.54). Higher armature stabilizes joints
+        # on Newton without affecting PhysX.
+        self.scene.robot.actuators["legs"].armature = preset(default=0.01, newton=0.03)
+        # Also bump damping on Newton — G1 hip/knee damping=5.0 is similar low-damp
+        # pattern that hurts Newton stability (same as Digit's low hip damping).
+        self.scene.robot.actuators["legs"].damping = preset(default=5.0, newton=20.0)
+
 
 @configclass
 class G1RoughEnvCfg_PLAY(G1RoughEnvCfg):