benchmark: add release parity harness

[gaelic-ghost]

Summary

• add a SwiftPM MaxVolBenchmark executable with deterministic fixture resources
• add uv-backed maxvolpy comparison and JSONL parity scripts
• document benchmark, parity, allocation-profiling workflow, and v0.9.0 performance plan

Validation

• swift build
• swift test
• swift build -c release --product MaxVolBenchmark
• .build/release/MaxVolBenchmark --iterations 2
• uv run --python 3.11 scripts/compare_maxvolpy.py --iterations 2
• python3 scripts/check_benchmark_parity.py /private/tmp/maxvol-swift-all.jsonl /private/tmp/maxvol-python-all.jsonl
• swift test -c release
• xcrun docc convert Sources/MaxVol/MaxVol.docc ...
• scripts/repo-maintenance/validate-all.sh

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 2b8d2409-46b4-4b67-9714-5dfc1d9b56af

📥 Commits

Reviewing files that changed from the base of the PR and between d3cbc2e and e6f6679.

📒 Files selected for processing (15)

• .gitignore
• Package.swift
• README.md
• ROADMAP.md
• Sources/MaxVol/MaxVol.docc/BenchmarkingAndParity.md
• Sources/MaxVol/MaxVol.docc/MaxVol.md
• Sources/MaxVolBenchmark/Resources/fixtures.json
• Sources/MaxVolBenchmark/main.swift
• Tests/MaxVolTests/FloatMaxVolTests.swift
• Tests/MaxVolTests/NumericalBehaviorTests.swift
• Tests/MaxVolTests/RectMaxVolTests.swift
• Tests/MaxVolTests/TestSupport.swift
• scripts/check_benchmark_parity.py
• scripts/compare_maxvolpy.py
• scripts/generate_benchmark_fixtures.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch benchmark/v0.8.0

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Check square coefficient magnitude during parity

For square MaxVol records, selected row count is always the matrix column count and reconstruction residual stays near zero for any nonsingular basis, so a regression that stops at the initial LU basis (for example the square-swap-3x2 case with maxIterations: 0) would still pass this checker even though its coefficient magnitude violates the MaxVol tolerance and differs from maxvolpy. Compare maxCoefficientMagnitude for square records (or against the square tolerance) before declaring parity.

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