Robot descriptions v2.17.0

Native ROS 2 installation and display

All four URDF packages now install with ament/colcon and include
display.launch.py, a saved RViz view, and joint sliders. Both robots expose
all six tools with jaw selection; standalone MSG and SSG48 expose both jaw
options. Headless viewing, external joint-state sources and simulated time
are supported.

Examples after installing and sourcing the workspace:

ros2 launch par6_description display.launch.py end_effector:=msg jaws:=soft_tpu
ros2 launch parol6_description display.launch.py end_effector:=ssg48 jaws:=fin_ray
ros2 launch msg_description display.launch.py jaws:=soft_tpu
ros2 launch ssg48_description display.launch.py jaws:=solid

ROS 2 launch resolves portable relative asset paths to installed package URIs
in memory. Existing model files, joint/frame conventions, geometry, colors,
collisions, kinematics, masses, COM, inertia and MuJoCo controls are retained.
ROS 1 entry points and the conditional catkin build path remain available.
RViz sliders publish visualization joint states; they are not a hardware driver.

The default RViz-compatible display description uses massless fixed child
frames for additional visuals, avoiding Humble/Jazzy RViz's per-link material
limitation. Original physical frames, joints, collisions and inertials are
preserved; rviz_materials:=false selects the original link/joint tree.

Humble and Jazzy Linux CI builds all four packages, relocates the install away
from source/build trees and checks all sixteen variants, nonzero external
joint-state TF, mimic joints, RViz/GUI startup and incompatible selections.
Integration logs and screenshots are saved as workflow artifacts. Tagged
releases require those ROS checks as well as the model build/tests.

The installation guide is bundled as docs/ROS2.md in every URDF download and
linked from product guides and READMEs. Model/assets/documentation licensing
remains CC BY 4.0; ROS support code remains Apache-2.0.