[lovasoa]

Fixes #82

Summary

Preserve whether a constraint was originally written with >=.

• HiGHS now emits greater-than constraints as native lower-bounded rows, preserving the solver's dual sign.
• Clarabel keeps its orientation metadata locally and negates only duals for constraints that were normalized from >=.
• ConstraintReference remains unchanged.
• Added a regression test covering the issue's model for both HiGHS and Clarabel.

Validation

• cargo fmt --all
• cargo test --features highs,clarabel
• cargo test --no-default-features --features highs,clarabel --test shadow_price
• cargo clippy --features highs,clarabel --all-targets -- -D warnings

[chatgpt-codex-connector]

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