Fix Isaac Sim app path routing

[RLRK-dev]

Summary

• route AppLauncher experience file lookup through the tracked root apps/ directory
• route render preset loading and its test through apps/rendering_modes
• remove the legacy Isaac Sim 5 apps/isaacsim_5 branch after that tree was removed
• add a 5.0.1 changelog entry and bump the isaaclab extension version

Rationale

Current develop no longer contains apps/isaacsim_5, but AppLauncher,
SimulationContext render presets, and the render preset test still branch to
that directory for Isaac Sim versions below 6. That makes the fallback path point
to files that are not present in the repository.

Validation

• git ls-tree origin/develop:apps shows only rendering_modes
• VIRTUAL_ENV=/home/rlrk/env_isaaclab6 ./isaaclab.sh -f
• ./isaaclab.sh -p -m py_compile source/isaaclab/isaaclab/app/app_launcher.py source/isaaclab/isaaclab/sim/simulation_context.py source/isaaclab/test/sim/test_simulation_render_config.py
• git diff --cached --check

[isaaclab-review-bot]

Code Review: Fix Isaac Sim app path routing

Summary

This PR removes dead code paths that referenced the non-existent apps/isaacsim_5 directory. The changes are well-scoped and necessary since the legacy Isaac Sim 5 app files were removed from the develop branch.

Findings

✅ Positive Observations

1. Correct cleanup of dead code: The apps/isaacsim_5 directory no longer exists in develop, so removing the branching logic prevents runtime failures from missing file paths.

2. Consistent changes across codebase: All three files (app_launcher.py, simulation_context.py, test_simulation_render_config.py) were updated consistently to use the unified apps/ path.

3. Proper versioning: The extension version bump (5.0.0 → 5.0.1) and changelog entry follow semantic versioning for a fix release.

4. Clean import removal: The unused get_isaac_sim_version import was properly removed from the test file.

📝 Observations

1. Method removal: The is_isaac_sim_version_5() method in app_launcher.py is being removed entirely. I verified this method has no external callers in the codebase, so this is safe.

2. Backward compatibility: Users running older Isaac Sim versions (< 6) will now use the same apps/rendering_modes path. This should be fine since the repository no longer contains version-specific files.

Validation Checklist

• Changes align with PR description
• Version bump follows semver (patch for bugfix)
• Changelog entry present and accurate
• Test file updated consistently with code changes
• No broken references to removed paths
• CI checks passing (labeler ✅)

Verdict

LGTM 👍 - Clean removal of obsolete version-branching logic. The changes are minimal, focused, and necessary to prevent file-not-found errors for users.

[AntoineRichard]

Hi @RLRK-dev — thank you so much for opening this PR, and for taking the time to contribute to Isaac Lab! 🙏

We're currently doing a big spring-clean of our pull request backlog, which had grown past 400 open PRs. Being honest: at that volume we stopped being able to give every contribution the attention it deserved, and this one is a case where we dropped the ball on getting back to you. That's on us, not on you.

Why this PR is being closed: Here is exactly what we found on this PR when we reviewed the backlog:

Opened	2026-05-11 (about 4 months ago)
Last commit on the branch	2026-05-11
Last activity from the author	about 4 months ago
Target branch	develop
Review status	Never reviewed by a maintainer — nobody on the team got to it. Sorry about that.
Merge status	Unknown
Size	1 commit(s), 5 file(s) changed, +12 / -38

It was picked up by the sweep because it is still marked as a draft, and it has been open for about 4 months. It was then put in the "close" bucket because the author has been silent for about 4 months — which is the signal we used to tell apart pull requests that are still being worked on from ones that have genuinely been set aside.

We deliberately did not close pull requests that were approved and ready to land, or that were small and clearly still fixing a live bug — there were 27 of those, and we are merging them rather than closing them.

To be completely clear — this is not a judgement on the quality or the value of your work. It's purely about getting the queue down to a size where we can actually review things properly and give contributors real, timely feedback.

One thing worth knowing first: Isaac Lab 3.0 has since shipped. develop is now at
3.0.0 while main is still at 2.3.2, and 3.0 restructured a fair amount — quaternion
conventions, actuator collections, data access, and the Isaac Sim extension imports all
changed. The migration guide
is the place to start if you rebase.

It is also the honest reason a lot of these older pull requests stopped applying: the code
they touched moved or was rewritten underneath them.

If this change is still relevant, please reopen this PR or open a fresh one against develop. With the backlog down to a reviewable size, it should get a response a lot sooner than this one did.

Thanks again for contributing to Isaac Lab, and sorry for the long silence! 💚

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🤖 This comment was drafted with AI assistance as part of a maintainer-led sweep of the Isaac Lab pull request backlog. A maintainer is behind this cleanup — but if this closure looks wrong, it may well be, so please push back and we'll take another look.