Refactor the URDF into multiple parts.

Makes it easier to work on an individual part in isolation.
Also change the vscode devconsole visualiser to one that works with includes

.devcontainer/Dockerfile

@@ -46,6 +46,11 @@ RUN apt-get update && apt-get install -y \
 #     ros-${ROS_DISTRO}-ament-lint-auto \
 #     ros-${ROS_DISTRO}-ament-lint-common
 
+# URDF / xacro tooling — needed to generate flat URDF for IDE preview
+RUN apt-get update && apt-get install -y \
+    ros-${ROS_DISTRO}-xacro \
+    ros-${ROS_DISTRO}-robot-state-publisher
+
 # Node.js for frontend development
 RUN curl -fsSL https://deb.nodesource.com/setup_22.x | bash - \
     && apt-get install -y nodejs