Add MuJoCo Robot Modeling Guide to Simulation Wiki

[FD-Shubham]

The article covers the full pipeline from physical robot design to a working MuJoCo simulation, including URDF and MJCF model authoring, physics parameter tuning, and testing strategies.

Value to the Knowledgebase:
MuJoCo is increasingly the standard simulator for robotics research and RL, but the learning curve for model authoring is steep. This article consolidates practical knowledge that is otherwise scattered across the MuJoCo docs, ROS wikis, and community forums, giving contributors a single reference to go from a CAD design to a simulation-ready robot.

[nevalsar]

Thank you for the contribution! Please rebase this branch onto the latest master branch and push again so the newly added PR validation workflow runs on this PR too.

I also found two blocking issues to address in the same update:

• Rename wiki/simulation/mujoco_robot_modeling.md to kebab-case (wiki/simulation/mujoco-robot-modeling.md) to satisfy markdown validation.
• Add the new MuJoCo page to wiki/simulation/index.md (it is currently in _data/navigation.yml but missing from the section index).

After rebasing and these fixes, I can re-review quickly.

[nevalsar]

@p-amyjiang for content review.

[p-amyjiang]

Hi team, good article so far. Requesting a few changes to improve flow:

• Move "Workflow: CAD to Simulation" to the top of the page to serve as an introduction/TLDR of the process.
• Physical Model Design references URDF and MJCF properties before those file formats are introduced and explained in the next section. Add an introduction to this section explaining why XML/URDF/MJCF are necessary in Mujoco and motivating the rest of the section on deciding the model design.
• Explain in text (~1 sentence) the difference between Mujoco Viewer and Programmatic Testing

[FD-Shubham]

Created a new PR:
#265