chore(release): prepare v3.1.0

[pumni]

Summary

• Prepare Sky Auto Player v3.1.0 with the curated changelog and release notes.
• Synchronize live version metadata and uv.lock to 3.1.0.
• Make the tag release body deterministic via the curated notes file.
• Record acceptance evidence for the native correctness, installer, Python, and frozen-build gates.

Release policy

• Native A/B benchmarking is not a release gate.
• The real SendInput CI qualification matrix is not a release gate.
• The post-send clock-failure cleanup uncertainty fix is covered by a dedicated Rust regression test.

Validation

• Ruff, Pyright, security audit: PASS
• Cargo fmt, check, clippy -D warnings, workspace tests: PASS
• rt_dispatch_no_alloc: PASS
• Native free-threaded wheel build and verification: PASS
• Python tests: 724 passed, 7 skipped, 1 xpassed
• Updater PowerShell 5.1 gate: PASS
• Pester: 61/61 passed
• Frozen v3.1.0 build, manifest, and packaged self-tests: PASS

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