ReservoirSeepageCoeffs struct
#include <gtopt/reservoir_seepage.hpp>
LP constraint coefficients for volume-dependent seepage.
The seepage LP constraint is: seepage_flow = slope × V_avg + constant where V_avg = (eini + efin) / 2 and constant is the y-intercept (the PLP file Constante field, matching Fortran FiltParam(PFiltConst)).
In matrix form: filt - slope*0.5*eini - slope*0.5*efin = constant
This matches PLP Filtracv (FILT_LINE mode): the RHS is set to the raw FiltConst value and the volume column coefficient to -pend * ScaleVol.