Handle state bounds as inequalities in iLQR

[markomiz]

Summary

• extend iLQR inequality buffers to include slots for static state bounds
• append state bound residuals and Jacobians during the backward sweep so the quadratic terms penalise bound violations
• update merit computation and multiplier handling to incorporate the new inequality entries

Testing

• cmake -S . -B build (fails: Eigen3Config.cmake not found in the environment)

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https://chatgpt.com/codex/tasks/task_e_68d1567bd6f4832ab690e1c8558522e8