feat(viser): overlay sim ground truth

[mustafab0]

Summary

• publish configured MuJoCo body poses on a sim-only typed stream
• extend VisualizationSpec with a truth/belief overlay hook
• render faint cyan truth ghosts beside solid planning obstacles in Viser
• show a toggle, legend, and live truth-vs-belief delta table
• enable Viser and six-object truth for xarm-room-sim

[greptile-apps]

Greptile Summary

This change adds an optional simulator ground-truth overlay to the Viser manipulation view. It publishes configured MuJoCo body poses, forwards them to the visualization, renders cyan truth markers with visibility controls and a truth-versus-belief distance table, and enables the feature for the xArm room simulation.

No defect was reproduced.

T-Rex validation blocked

• Missing package: The targeted Python harness could not import the project runtime because the git Python module from the GitPython package is unavailable.
• Missing tool: The xArm room simulation asset is stored as a Git-LFS pointer and git-lfs is unavailable, so the configured MuJoCo body names could not be checked against the real room scene.

Confidence Score: 5/5

No verified implementation defect blocks merging.

There are no final severity-bearing findings. Source tracing confirms that matching typed pose streams, visualization forwarding, overlay configuration, marker lifecycle, and cleanup handling are present; the environment prevented execution against the packaged xArm room scene.

Files Needing Attention: If the simulation environment is available, dimos/simulation/engines/mujoco_sim_module.py and dimos/robot/manipulators/xarm/blueprints/simulation.py merit a final runtime check against the Git-LFS-backed xArm room asset.

T-Rex Logs

What T-Rex did

• I ran a fake-backed verification harness to exercise the generated stream connection, MuJoCo pose publication and rate limiting, Viser marker lifecycle, and report forwarding to the visualizer, but import resolution stopped at a missing git Python package before assertions could run.
• I attempted to inspect the xArm room asset, but it is a Git-LFS pointer and the git-lfs tool is unavailable.
• The harness run produced no severity-bearing findings and was blocked before assertions due to tooling limitations.

_{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "feat(viser): overlay sim ground truth" | Re-trigger Greptile}