Add C++ API reference to Sphinx docs

[bdice]

Summary

Integrate cuML’s Doxygen-generated C++ API into the Sphinx documentation using Breathe. This adds namespace references for ML, MLCommon, and cuml::genetic to the main documentation navigation and normalizes Doxygen 1.9.1 XML constructs that Sphinx cannot represent.

[coderabbitai]

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ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: b9fc6c17-2ece-428d-91be-141cf83b9c78

📥 Commits

Reviewing files that changed from the base of the PR and between 4203a08 and 2120ad5.

📒 Files selected for processing (13)

• .gitignore
• conda/environments/all_cuda-129_arch-aarch64.yaml
• conda/environments/all_cuda-129_arch-x86_64.yaml
• conda/environments/all_cuda-133_arch-aarch64.yaml
• conda/environments/all_cuda-133_arch-x86_64.yaml
• cpp/Doxyfile.in
• dependencies.yaml
• docs/source/conf.py
• docs/source/cpp/genetic.rst
• docs/source/cpp/index.rst
• docs/source/cpp/ml.rst
• docs/source/cpp/mlcommon.rst
• docs/source/index.rst

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📝 Walkthrough

Summary by CodeRabbit

• Documentation

  • Added a C++ API documentation section covering ML, MLCommon, and genetic namespaces.
  • Integrated generated C++ API references into the documentation navigation.
  • Enabled Doxygen XML generation and Sphinx integration for richer API documentation.

• Chores

  • Added required documentation tooling to supported CUDA environments.
  • Excluded generated Doxygen XML artifacts from version control.

Walkthrough

Changes

C++ API documentation

Layer / File(s)	Summary
Doxygen XML generation and dependencies .gitignore, cpp/Doxyfile.in, dependencies.yaml, conda/environments/*	Doxygen XML generation is enabled. breathe is added to documentation dependencies. The generated XML directory is ignored.
Doxygen XML cleanup and Breathe configuration docs/source/conf.py	Sphinx registers Breathe and maps the cuML XML output. clean_doxygen_xml removes unsupported or conflicting XML elements and repairs enum-value IDs before documentation processing.
C++ API documentation pages docs/source/cpp/*, docs/source/index.rst	The documentation tree adds C++ API pages for the ML, MLCommon, and cuml::genetic namespaces.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 2120a

This PR adds C++ API documentation and the required documentation dependency without introducing an identified correctness, security, availability, or deployment risk; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: dantegd, gforsyth, betatim

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (12 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding the C++ API reference to the Sphinx documentation.
Description check	✅ Passed	The description directly explains the Breathe integration, documented namespaces, navigation updates, and Doxygen XML normalization.
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 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (12 skipped: 12 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[jcrist]

We don't currently consider the C++ api public in any way - I'd worry about the effect of publishing the docs for something that we make no promise is usable outside of the python library (and no promises of deprecations/no breaking changes). Personally I wouldn't want these docs to be published at this point.

cc @csadorf for another opinion.