Fix PrismaticJoint (trunk) control: IdealPDActuator with high stiffness

Replace ImplicitActuator (which doesn't work for prismatic joints) with
IdealPDActuator. This bypasses PhysX drive and explicitly computes PD forces
using set_dof_actuation_forces().

Changes:
- stiffness=100k, damping=5k to resist arm reaction forces (~150N) with <2mm deflection
- Read trunk_cmd from ArticulationCfg initial position (single source of truth)
- Integrate trunk diagnostics into robot state output
- Remove hardcoded trunk_target parameter

source/mindbot/mindbot/tasks/manager_based/il/open_drybox/mindrobot_2i_cfg.py

@@ -61,11 +61,11 @@ MINDBOT_CFG = ArticulationCfg(
             # NOTE: pos z = 0.44 (base clearance) + PrismaticJoint value.
             # If you change PrismaticJoint, update pos z accordingly to avoid
             # geometry clipping that causes the robot to fall on spawn.
-            "PrismaticJoint": 0.4,
+            "PrismaticJoint": 0.2,
             "head_pitch_Joint": 0.0,
             "head_yaw_Joint": 0.0,
         },
-        pos=(0.001, 0.001, 0.74),  # z = 0.44 (base clearance) + 0.26 (PrismaticJoint)
+        pos=(0.001, 0.001, 0.7),  # z = 0.44 (base clearance) + 0.26 (PrismaticJoint)
     ),
     actuators={
         # RM-65 J1-J3: shoulder/elbow — max 180°/s ≈ 3.14 rad/s
@@ -110,13 +110,14 @@ MINDBOT_CFG = ArticulationCfg(
         # IdealPDActuator: explicitly computes F = k_p*(target-pos) + k_d*(target_vel-vel)
         # and sends via set_dof_actuation_forces(), bypassing PhysX drive which
         # doesn't work correctly for prismatic joints with set_dof_position_targets().
-        # NOTE: trunk gravity is disabled in USD, so moderate stiffness is sufficient.
-        "trunk": ImplicitActuatorCfg(
+        # NOTE: trunk gravity disabled by startup event. High stiffness to resist
+        # arm reaction forces (~150N) — deflection < 2mm at 100k stiffness.
+        "trunk": IdealPDActuatorCfg(
             joint_names_expr=["PrismaticJoint"],
-            effort_limit=100.0,
-            velocity_limit=0.2,
+            effort_limit=2000.0,
+            velocity_limit=0.5,
             stiffness=100000.0,
-            damping=10000.0,
+            damping=5000.0,
         ),
         "wheels": ImplicitActuatorCfg(
             # joint_names_expr=[".*_revolute_Joint"],