Add option for shearLayerAdapted LES length scale

[yifan-flex]

Note

Low Risk
Small schema expansion (new enum value) plus a focused validation test; risk is mainly downstream consumers needing to handle the new string value.

Overview
Adds a new DetachedEddySimulation.grid_size_for_LES option, shearLayerAdapted, expanding the allowed LES length-scale choices and updating the field documentation accordingly.

Extends test coverage to assert the new option is accepted and invalid values still fail validation.

^{Written by Cursor Bugbot for commit 6da6bb7. This will update automatically on new commits. Configure here.}