fix(local_hammer_nail): make the board/nail USDs render, and publish the wall variant

assets/local_hammer_nail/board_nail_wall.urdf

@@ -0,0 +1,64 @@
+<?xml version="1.0"?>
+<!-- Wall + horizontal nail for hammer_insert_nail_wall, as a URDF so IsaacLab's
+     UrdfConverter can produce the articulated USD the IsaacSim backend needs
+     (metasim's isaac handler spawns ArticulationObjCfg from a USD, not an MJCF).
+     Mirrors the MuJoCo board_nail_wall.xml: a fixed upright wall with a nail on a
+     HORIZONTAL prismatic joint (nail_drive, axis -x => driven +x into the wall).
+     Used for RENDERING only (physics stays MuJoCo in the hybrid path); the joint
+     must exist so metasim can mirror the nail's slide into the IsaacSim render
+     each frame. URDF cylinders default to the z axis, so the nail shaft/head are
+     pitched 90 deg (rpy 0 1.5708 0) to lie along x, matching the MJCF fromto. -->
+<robot name="board_nail_wall">
+  <link name="wall">
+    <visual>
+      <origin xyz="0.03 0 0.15" rpy="0 0 0"/>
+      <geometry><box size="0.06 0.30 0.30"/></geometry>
+      <!-- brick texture (mirrors the MJCF cube material); IsaacLab's UrdfConverter
+           bakes it into the render-only USD. Falls back to the color if unsupported. -->
+      <material name="brick">
+        <color rgba="0.62 0.32 0.26 1"/>
+        <texture filename="textures/wall_brick.png"/>
+      </material>
+    </visual>
+    <collision>
+      <origin xyz="0.03 0 0.15" rpy="0 0 0"/>
+      <geometry><box size="0.06 0.30 0.30"/></geometry>
+    </collision>
+    <inertial>
+      <origin xyz="0.03 0 0.15" rpy="0 0 0"/>
+      <mass value="0.5"/>
+      <inertia ixx="4e-3" iyy="2e-3" izz="2e-3" ixy="0" ixz="0" iyz="0"/>
+    </inertial>
+  </link>
+
+  <link name="nail">
+    <visual>
+      <origin xyz="0 0 0" rpy="0 1.5708 0"/>
+      <geometry><cylinder radius="0.003" length="0.06"/></geometry>
+      <material name="steel"><color rgba="0.72 0.72 0.75 1"/></material>
+    </visual>
+    <visual>
+      <origin xyz="-0.0325 0 0" rpy="0 1.5708 0"/>
+      <geometry><cylinder radius="0.009" length="0.005"/></geometry>
+      <material name="steel_head"><color rgba="0.70 0.70 0.74 1"/></material>
+    </visual>
+    <collision>
+      <origin xyz="-0.0325 0 0" rpy="0 1.5708 0"/>
+      <geometry><cylinder radius="0.009" length="0.005"/></geometry>
+    </collision>
+    <inertial>
+      <origin xyz="0 0 0" rpy="0 0 0"/>
+      <mass value="0.04"/>
+      <inertia ixx="2e-6" iyy="2e-5" izz="2e-5" ixy="0" ixz="0" iyz="0"/>
+    </inertial>
+  </link>
+
+  <joint name="nail_drive" type="prismatic">
+    <parent link="wall"/>
+    <child link="nail"/>
+    <origin xyz="0 0 0.09" rpy="0 0 0"/>
+    <axis xyz="-1 0 0"/>
+    <limit lower="-0.04" upper="0.0" effort="100" velocity="1.0"/>
+    <dynamics friction="15.0" damping="10.0"/>
+  </joint>
+</robot>

assets/local_hammer_nail/board_nail_wall.xml

@@ -0,0 +1,61 @@
+<mujoco model="board_nail_wall">
+  <!-- Wall + horizontal nail for the hammer_insert_nail_wall task, the HORIZONTAL
+       sibling of board_nail.xml. The nail hangs off a fixed upright WALL by a
+       single HORIZONTAL slide joint with dry friction (frictionloss), driven
+       along +x INTO the wall by a hammer strike.
+
+       Why a wall (vs the tabletop board): the slide axis lies in the table plane,
+       so gravity (-z) is PERPENDICULAR to the only free DOF and is fully absorbed
+       by the joint constraint — the nail can NEVER creep in on its own, no matter
+       how soft the friction constraint. Only a horizontal strike whose impulse
+       exceeds the frictionloss drives it. (The vertical board_nail needs a stiff
+       solreffriction to stop gravity sag; here gravity does no work along x.)
+
+       Modeling notes (mirror board_nail.xml):
+       - nail SHAFT collision OFF (contype=0/conaffinity=0): its going "into the
+         wall" is faked by the slide joint, so it must not fight real contact with
+         the wall. Only the nail HEAD keeps collision — the surface the hammer
+         strikes (from the -x / robot side, pushing +x into the wall).
+       - damping spreads the drive over several strikes (one blow does not bottom
+         it out); armature kills passive creep; solreffriction stiffens the
+         friction constraint (harmless here, kept for parity with board_nail).
+       - Loaded as ArticulationObjCfg(fix_base_link=True); the root "wall" body
+         carries no pos/quat (set via cfg default_position). The wall's near face
+         (toward the robot) is at the root origin (x=0), so the nail body origin
+         starts flush with the face and drives +x into the wall.
+       - Success is read from the nail body world x (insertion depth along +x):
+         nail_drive 0 = flush at the face, range floor -0.04 = fully driven. -->
+  <compiler angle="radian"/>
+  <asset>
+    <!-- Real brick-wall image texture (running-bond bricks + mortar + speckle),
+         generated once and shipped next to this MJCF. Mapped onto the wall box so
+         it reads as an actual brick wall rather than a flat colour. The nail HEAD
+         and SHAFT keep flat rgba (metal). -->
+    <!-- type="cube" (not "2d"): MuJoCo maps a 2d texture onto box faces degenerately
+         (one row stretched into vertical stripes); a cube texture paints the full
+         brick image on every face. The PNG is pre-rotated so courses run horizontal. -->
+    <texture name="wall_brick_tex" type="cube" file="textures/wall_brick.png"/>
+    <material name="wall_brick_mat" texture="wall_brick_tex" texuniform="false"
+              texrepeat="1 1" rgba="1 1 1 1" specular="0.05" shininess="0.05"/>
+  </asset>
+  <worldbody>
+    <body name="wall">
+      <!-- Upright brick wall standing on the table: 6 cm thick (x) x 30 cm wide (y)
+           x 30 cm tall (z); near face at x=0 (robot side), far face at x=0.06. The
+           near face is kept at x=0 so the nail rest world x (and thus the checker's
+           along-x gate) is unchanged when the wall is resized. -->
+      <geom name="wall" type="box" size="0.03 0.15 0.15" pos="0.03 0 0.15"
+            material="wall_brick_mat" friction="0.9 0.05 0.001" density="500"/>
+      <body name="nail" pos="0 0 0.09">
+        <joint name="nail_drive" type="slide" axis="-1 0 0" range="-0.04 0"
+               frictionloss="15" damping="10" armature="0.05" solreffriction="0.004 1"/>
+        <!-- shaft along x: from +0.03 (into wall) to -0.03 (sticking toward robot) -->
+        <geom name="nail_shaft" type="cylinder" fromto="0.03 0 0 -0.03 0 0" size="0.003"
+              density="7850" contype="0" conaffinity="0" rgba="0.72 0.72 0.75 1"/>
+        <!-- head: a disk at the robot-facing (-x) end; the hammer strike surface -->
+        <geom name="nail_head" type="cylinder" fromto="-0.03 0 0 -0.035 0 0" size="0.009"
+              density="7850" solref="0.004 1" solimp="0.9 0.95 0.001" rgba="0.70 0.70 0.74 1"/>
+      </body>
+    </body>
+  </worldbody>
+</mujoco>