Add renderer info query API

[devshahofficial]

Split out from #3254 in response to Haroon's request for smaller Filament PRs.

Summary

• Adds mjrRendererInfo plus mjr_defaultRendererInfo and mjr_getRendererInfo to report the active renderer family and graphics backend.
• Reports classic as classic / opengl, noop as noop / none, and Filament as filament with its selected backend.
• Adds Python raw alias, pybind struct exposure, render function bindings, introspection metadata, and a binding smoke test.

Validation

• git diff --check
• python3 -m py_compile python/mujoco/introspect/functions.py python/mujoco/introspect/structs.py python/mujoco/bindings_test.py
• PYTHONPATH=/tmp/mujoco-check-pydeps:python/mujoco python3 python/mujoco/codegen/generate_function_traits.py >/tmp/mujoco-function-traits-check.h
• PYTHONPATH=/tmp/mujoco-check-pydeps:python/mujoco python3 python/mujoco/codegen/generate_enum_traits.py >/tmp/mujoco-enum-traits-check.h
• cmake -S . -B /tmp/mujoco-renderer-info-build -DMUJOCO_BUILD_TESTS=ON -DMUJOCO_TEST_PYTHON_UTIL=OFF -DCMAKE_BUILD_TYPE=Release
• cmake --build /tmp/mujoco-renderer-info-build --target mujoco -j2

Notes

• Draft PR: full Python wheel/binding build was not completed locally; standalone Python CMake expects setup.py's copied source layout.
• backend_version is reserved and currently returns an empty string until backend-specific version extraction is added.

[BlGene]

I guess once this PR is merged, wheels will be built, and the render version will be queryable?

Leaving a note here so I get updated.

Looking forward to this functionality. 🙌

[haroonq]

Thanks!

[devshahofficial]

Rebased this onto current main and marked it ready.

Validated with:

• git diff --check
• python3 -m py_compile python/mujoco/introspect/functions.py python/mujoco/introspect/structs.py python/mujoco/bindings_test.py
• PYTHONPATH=/tmp/mujoco-pr3340-pydeps:python/mujoco python3 python/mujoco/codegen/generate_function_traits.py >/tmp/mujoco-pr3340-function-traits.h
• PYTHONPATH=/tmp/mujoco-pr3340-pydeps:python/mujoco python3 python/mujoco/codegen/generate_enum_traits.py >/tmp/mujoco-pr3340-enum-traits.h
• cmake -S . -B /tmp/mujoco-pr3340-build -DMUJOCO_BUILD_TESTS=ON -DMUJOCO_TEST_PYTHON_UTIL=OFF -DCMAKE_BUILD_TYPE=Release
• cmake --build /tmp/mujoco-pr3340-build --target mujoco -j2
• small ctypes smoke against the built libmujoco.dylib: mjr_getRendererInfo returns classic, empty backend, empty backend version before a context exists.

I also tried a narrow Filament/MJR-compat configure. It still hits the separate dear_imgui/SDL2 source-build issue covered by #3252, so I’m not mixing that fix into this API PR.

[devshahofficial]

Rebased this onto current main and fixed the conflict in filament_context.cc. The resolution keeps both sides: upstreams larger Filament command buffers and this PRs stored backend_ for the renderer info API.

Local validation:

• git diff --check
• python3 -m py_compile python/mujoco/introspect/functions.py python/mujoco/introspect/structs.py python/mujoco/bindings_test.py
• PYTHONPATH=python/mujoco python/mujoco/codegen/generate_function_traits.py in a fresh venv

@haroonq once fresh CI goes green again, I think this is unblocked for submit. 🙏

[devshahofficial]

Thanks for the reviews. One thing I can’t inspect from the fork side: feedback/copybara is failing on cl/945632454 after the approvals, while the public matrix is green.

@haroonq / @mmossg, could one of you check whether that internal failure needs a code tweak from me or just an internal retry/submit-side fix?

[devshahofficial]

Quick update: feedback/copybara is green now, and the public matrix is clean too. I do not see anything left to patch from my side, so this looks ready to submit whenever you’re good with it. cc @haroonq @mmossg

[haroonq]

Yes, the issue is on our end and I'm investigating. It's a little unclear why it's not working at the moment, but hopefully we can resolve it soon.

Thanks for your contributions! It is appreciated.