# Description

This PR fixes an issue where only one `FrameTransformer` instance could
visualize its connecting line between source and target frames. The
problem stemmed from a shared global `debug_draw` interface, where each
instance's call to `clear_lines()` would erase the lines drawn by
others.

The solution replaces `debug_draw` with a per-instance
`VisualizationMarkers`-based renderer that uses a thin yellow cylinder
to depict the connecting line. This ensures that all active
`FrameTransformer` instances in a scene can render their lines
concurrently without interfering with each other.

Fixes #2525, #1754

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

## Screenshots

| Before | Now |
|---------|----------|
| <img
src="https://github.com/user-attachments/assets/c6a3f496-4c11-44b1-a3d3-e1af5ae5e4b0"
width="500"/> | <img
src="https://github.com/user-attachments/assets/89342fab-73c1-470d-8a63-0a45c11b3aa8"
width="500"/> |

Only the most recently added `FrameTransformer` line would appear. After
this change, all relevant connections are visualized concurrently.

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] 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
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Co-authored-by: Kelly Guo <kellyg@nvidia.com>