Evaluate whether solvent_floor and min_halflife fields belong in the public API.

[boulderdaze]

Those two fields were added in aerosol.hpp to support the musica tutorials.

std::optional<double> solvent_floor_;
std::optional<double> min_halflife_;

At the moment, these two fields are not wired into the configuration system. There are no corresponding YAML keys, the configuration parser does not populate them, and validate.cpp does not include any validation logic for them.

Evaluate whether these fields belong in the public API. They may exist solely to support the current solver's numerical stability and may not make sense as user-configurable options.