Fixes cloner to skip cloning the source environment.

[ooctipus]

Description

Cloning the source environment can leads to some unexpected bug, this PR skips the cloning source environment during usd_replicate and physx_replicate

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Summary

This PR fixes a critical bug where cloning environments could cause self-replication when the source environment path matches a destination path. The fix prevents Sdf.CopySpec and PhysX replication from copying a prim onto itself, which would create duplicate PhysX bodies and cause erratic joint behavior.

Key Changes:

• usd_replicate: Added explicit guard to skip Sdf.CopySpec when src == dp
• physx_replicate: Extracts environment ID from source path using template structure and filters it from target worlds list
• Added comprehensive tests with parametrized cases covering self-world exclusion scenarios
• Properly documented in changelog with version bump to 4.2.1

The implementation is clean, well-tested, and follows semantic versioning conventions.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The fix directly addresses a specific bug with clear logic. Tests provide comprehensive coverage of the edge cases, including self-world scenarios and external templates. The changes are minimal, focused, and properly documented.
• No files require special attention

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/cloner/cloner_utils.py	Added guard to skip Sdf.CopySpec when source equals destination, preventing redundant self-copy operations
source/isaaclab_physx/isaaclab_physx/cloner/physx_replicate.py	Extracts environment ID from source path and filters it from target worlds to prevent PhysX body duplication
source/isaaclab/test/sim/test_cloner.py	Added comprehensive parametrized tests verifying self-copy prevention in both USD and PhysX replication paths

_{Last reviewed commit: 01f0449}

[greptile-apps]

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