refactor: remove robot asset-directory overrides

[jiwenc-nv]

Description

Stacked on #1114; merge that first.

Remove the SO101 and reBot asset-directory environment overrides and use the standard cache locations. Simplify the shared cache helper and update the robot visualization and migration documentation. Asset fetching and checksum validation are unchanged.

Type of change

• 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 change)
• Documentation update

Testing

Focused temporary assertions passed for both robots with default/empty/XDG cache roots, ignored legacy and current robot overrides, wrapper copying, and local reBot cache validation. No permanent tests added for this small configuration removal.

make current-docs passed after rebasing onto #1114 at 1598a94f. Full pre-commit is blocked by an inherited stale :code-dir: reference to src/compat/isaacteleop in the build guide (the alias is now src/compat/isaacteleop.py). It also auto-fixes an inherited SVG EOF newline; that unrelated change is excluded.

Checklist

• I have read and understood the contribution guidelines
• I have run the linter and formatter with SKIP=check-copyright-year pre-commit run --all-files
• I have made corresponding changes to the documentation
• I have added tests that prove my fix/feature works (or explained why not)
• I have signed off all my commits (git commit -s) per the DCO

Summary by CodeRabbit

• Updates

  • SO-101 and reBot assets now use the standard cache location: XDG_CACHE_HOME when set, or ~/.cache otherwise, under an isaaccapture subdirectory.
  • The asset-directory override variables for these robots are no longer supported. The ISAAC_TELEOP_* runtime switches keep their existing names.

• Documentation

  • Updated the migration guide with the cache location change and removed override support. The robot visualization guide no longer includes asset-fetching and cache setup details.

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📝 Walkthrough

Walkthrough

The SO-101 and reBot asset cache paths no longer accept their individual environment-variable overrides. The cache helper uses nonblank XDG_CACHE_HOME, or ~/.cache when it is blank, and appends isaaccapture/<name>. The migration guide records the removed overrides and unchanged ISAAC_TELEOP_* runtime switch names. The robot visualization README no longer includes asset-fetching instructions.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: 🔵 Low · up to 3ea41

Offline users upgrading with assets stored only in a removed override directory may be unable to load them until the cache is moved. The impact is limited and recoverable, but the migration note should explain the step.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 1 files. (2 skipped: 2…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: removal of robot asset-directory overrides.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 1 files. (2 skipped: 2 unsupported.)

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✨ Finishing Touches 💡 1

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Actionable comments posted: 1

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Inline comments:
Review comments at @docs/source/references/migration.rst:
- Around line 113-114: Update the migration note about removed SO101 and reBot
asset-directory overrides to state that users with usable caches only in those
directories must move them to the corresponding new default cache directory
before offline use. Keep the existing runtime-switch naming information
unchanged.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: NVIDIA/IsaacCapture/.coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: a1e901bf-eaeb-4afa-8a6c-feb6b000dde2

📥 Commits

Reviewing files that changed from the base of the PR and between 18a06de and 3ea4128.

📒 Files selected for processing (4)

• docs/AGENTS.md
• docs/source/references/migration.rst
• examples/robot_viz/README.md
• src/python/isaaccapture/viz/robot/assets.py

💤 Files with no reviewable changes (1)

• examples/robot_viz/README.md

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