perf: improve trench algorithm performance and continuity

[otto-link]

Improve the performance and output quality of the trench algorithm.

• The algorithm is significantly slower than other comparable terrain algorithms.
• Steep paths can produce visible discontinuities or artifacts along the trench.
• Investigate the main performance bottlenecks and optimize the implementation.
• Ensure the trench profile remains smooth and continuous, particularly along steep or rapidly changing paths.

The goal is to bring trench performance closer to comparable algorithms while producing stable, continuous results on steep paths.