Add coordinated placement atomic action demo

[skywhite1024]

Description

This PR adds CoordinatedPlacement, an object-centric dual-arm atomic action for the case where both arms already hold objects: the support arm moves and keeps holding the support object, while the placing arm aligns its held object above the support target, releases it, and retreats.

The update also adds a bread-on-pan tutorial scenario, target-axis visualization, and a full-frame GIF in the built-in atomic actions documentation so reviewers can inspect the behavior loop directly.

Dependencies: none beyond the existing simulation/tutorial dependencies.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which improves an existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (existing functionality will not work without user modification)
• Documentation update

Screenshots

See docs/source/_static/atomic_actions/coordinated_placement.gif and the CoordinatedPlacement row in docs/source/overview/sim/atomic_actions/builtin_actions.md.

Notes

• CoordinatedPlacementTarget explicitly carries both placing/support HeldObjectState values instead of relying on the single-slot WorldState.held_object to represent dual held objects.
• On success, WorldState.held_object is updated to the support object's held state, normalized to batched tensor shapes, because the placing object has been released while the support object remains held.
• The tutorial draws target axes at the support/placing object target poses and records from a fixed camera facing the table front.

Checklist

• I have run the black . command to format the code base.
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Dependencies have been updated, if applicable.

Tests

• /home/dex/miniconda3/envs/embodichain040/bin/black embodichain/lab/sim/atomic_actions/actions.py scripts/tutorials/atomic_action/coordinated_placement.py scripts/tutorials/atomic_action/tutorial_utils.py tests/sim/atomic_actions/test_actions.py
• /home/dex/miniconda3/envs/embodichain040/bin/python -m pytest tests/sim/atomic_actions/test_actions.py -q
• PYTHONUNBUFFERED=1 /home/dex/miniconda3/envs/embodichain040/bin/python scripts/tutorials/atomic_action/coordinated_placement.py --headless --headless_play --diagnose_plan --device cuda
• PYTHONUNBUFFERED=1 /home/dex/miniconda3/envs/embodichain040/bin/python scripts/tutorials/atomic_action/coordinated_placement.py --auto_play --device cuda