MaxVol v0.8.0

What changed

• Added the SwiftPM MaxVolBenchmark executable with deterministic bundled fixtures.
• Added uv-backed maxvolpy comparison and JSONL parity checking scripts.
• Refactored duplicated Swift Testing helpers into shared test support.
• Documented benchmark, parity, and allocation-profiling workflows.
• Added the v0.9.0 evidence-driven performance plan to ROADMAP.md.

Verification

• swift build
• swift test
• swift build -c release --product MaxVolBenchmark
• Release benchmark JSONL compared against maxvolpy for 20 result keys
• swift test -c release
• DocC conversion completed; warnings were from dependency symbol graphs
• scripts/repo-maintenance/validate-all.sh