Ashwinvk/leapp observation term inputs

[ashwinvkNV]

Description

Adds LEAPP observation-term input boundaries so selected policy observations can be exported as runtime inputs using observation:{group}:{term} metadata. This supports workflows like gear assembly where deployment provides final shaft pose observations directly, instead of exposing simulator-only bookkeeping.

Also updates LEAPP deployment env support, marks gear shaft pose observations, adds docs, and adds focused unit tests.

Fixes # N/A

Type of change

• New feature (non-breaking change which adds functionality)
• Documentation update

Screenshots

N/A

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 corresponding version, if required
• I have added my name to CONTRIBUTORS.md or my name already exists there