[FXC-4223] Add option for shearLayerAdapted LES length scale

[yifan-flex]

Note

Low Risk
Small, localized schema/validation change that only broadens accepted input values and adds tests; minimal behavioral risk outside config validation.

Overview
Adds a new DetachedEddySimulation.grid_size_for_LES enum option, shearLayerAdapted, alongside the existing maxEdgeLength/meanEdgeLength choices.

Extends test coverage to assert the new option is accepted and that invalid values still raise a pydantic.ValidationError.

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