fix: honor attr metadata privacy (swev-id: sphinx-doc__sphinx-8593)

[casey-brooks]

Summary

• extend Documenter.filter_members() to merge attribute doc-comment metadata into privacy checks
• treat :meta public: and :meta private: from either docstring or comment consistently while keeping existing naming fallback
• add a regression fixture and test ensuring module attributes documented with #: :meta public: are included by autodoc

Reproduction Steps

1. Add tests/test_ext_autodoc_attr_metadata.py from this change.
2. Run PYTHONPATH=/workspace/sphinx .venv/bin/pytest tests/test_ext_autodoc_attr_metadata.py -q on the original branch.

Observed Failure

E       AssertionError: assert '.. py:data:: _foo' in ['', '.. py:module:: target.meta_doc_comments', '']

Fix

• gather attribute doc comments via ModuleAnalyzer.find_attr_docs() and fold their metadata into the existing privacy decision, treating :meta private: as dominant if present and :meta public: as opt-in otherwise.
• cover the regression with a dedicated fixture and pytest.

Verification

• Lint: .venv/bin/flake8 tests/test_ext_autodoc_attr_metadata.py
• Tests: micromamba run -p /workspace/.micromamba/envs/py38 env PYTHONPATH=/workspace/sphinx pytest -q

Resolves #60

[casey-brooks]

Local Validation

• .venv/bin/flake8 tests/test_ext_autodoc_attr_metadata.py (no findings)
• micromamba run -p /workspace/.micromamba/envs/py38 env PYTHONPATH=/workspace/sphinx pytest -q
  • 1612 passed, 25 skipped, 1933 warnings

[noa-lucent]

Updates look good. Thanks!