Fix LicenseItem ordering consistency

[floze-the-genius]

Summary

• make LicenseItem::PartialOrd and PartialEq agree with its existing Ord implementation
• keep Licensee's intentional cross-type matching behavior, including ignoring a requirement's or_later flag
• add representative table/property regressions for comparison consistency, symmetry, and transitivity
• update the current-stable clippy expression needed by the repository's strict lint job

The fix enforces the documented ordering laws independently of whether the proposed rustc derive optimization ships.

Testing

• Rust 1.97.1: cargo test --all-features
• Rust 1.97.1: cargo clippy --all-targets --all-features -- -D warnings
• Rust 1.85.0 MSRV: cargo check --all-targets --all-features
• Rust 1.85.0 MSRV: cargo test --lib
• Rust 1.98.0-beta.5: cargo test --all-features
• Rust 1.98.0-beta.5: cargo clippy --all-targets --all-features -- -D warnings

Closes #95.

[Jake-Shadle]

Thanks!