feat(diskann): expose cross-platform Python update APIs

[ScissorJack-ever]

Description

Expose standalone DiskANN build, search, and update APIs to Python, using external IDs for all public update operations.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Performance improvement
• Code refactoring
• Documentation update
• CI/CD changes

Changes Made

• Added Python bindings for DiskANN build, open, search, insert, batch insert, remove, batch remove, flush, and external-ID lookup.
• Added external-ID validation and mapping persistence across insert, delete, flush, and reload.
• Added macOS update support using pread, pwrite, ftruncate, and fsync.
• Added Windows update support using overlapped ReadFile/WriteFile, file resizing, and FlushFileBuffers.
• Allowed Windows IOCP search handles to coexist with the writable update handle.
• Added a dedicated DiskANN CMake dependency target, independent from LASER.
• Made libcoro available on every supported platform while keeping liburing Linux-only.
• Fixed Linux ARM wheel imports by linking libaio even when LASER is disabled.
• Restored tombstone and external-ID state for read-only reloads.
• Added portable C++ update coverage and enabled Python update tests on all wheel platforms.
• Fixed io_uring E2E tests to distinguish blocking-backend validation from reactor-specific result validation.

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed

cmake --build build/Verify --target test_diskann_portable_update
ctest --test-dir build/Verify -R 'test_diskann_(portable_update|disk_page_io)$' --output-on-failure

python -m pytest python/tests/diskann/test_update.py -q

cmake --build build/Verify --target _alayalitepy
cmake --build build/VerifyNoLaser --target _alayalitepy

build/Verify/tests/diskann/test_diskann_update_e2e \
  --gtest_filter='UpdateE2ETest.PipelinedSearch*'

Results:

• Python DiskANN update tests: 6 passed.
• Portable DiskANN update test: passed.
• Existing DiskPageIO tests: passed.
• Blocking pipelined-search contract test: passed.
• Reactor result-equivalence test: skipped when io_uring is unavailable.
• Python extension builds successfully with LASER both enabled and disabled.
• LASER-disabled extension correctly records libaio as a runtime dependency.
• All configured commit hooks passed.

Checklist

• My code follows the project's coding style
• I have run the configured lint and commit hooks
• I have added tests that prove my fix/feature works
• I have run the complete make test suite
• Documentation changes are not required
• My commits follow the conventional commits format

Additional Notes

• Regular DiskANN updates now use a portable blocking backend on macOS and Windows.
• search_pipelined() remains a Linux io_uring-specific optimization and intentionally does not silently fall back to blocking I/O.
• Native macOS and Windows wheel jobs provide the final platform-specific compilation and runtime verification.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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