Allow 2GB values

[qdequele]

Summary

• raise overflow sanity check from 1GB to 2GB
• update validation example to mention 2GB
• adjust large value validation test to expect new 2GB limit
• fix clippy warnings in numa module and remove stray doc comment

Testing

• cargo build --release
• cargo clippy --all-targets --all-features -- -D warnings (fails to finish in reasonable time)
• cargo test --release (fails to finish building full suite in this environment)
• cargo bench (not executed due to long build time)

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https://chatgpt.com/codex/tasks/task_b_687b4e9f63c8832696b947d44478ac1e