An EqState as the generic param list. Bands flatten to band.{i}.* control ids
(type · freq · gain · q · on); the optional HPF/LPF to hpf.*/lpf.*. The band count and
filter presence are recoverable from which ids exist, so the CONTROL surface round-trips
losslessly (paramsToEq). Band identity (id) and display (name/label) are not
controls, so they are not carried here — a param round-trip re-derives positional ids.
An EqState as the generic param list. Bands flatten to
band.{i}.*control ids (type · freq · gain · q · on); the optional HPF/LPF tohpf.*/lpf.*. The band count and filter presence are recoverable from which ids exist, so the CONTROL surface round-trips losslessly (paramsToEq). Band identity (id) and display (name/label) are not controls, so they are not carried here — a param round-trip re-derives positional ids.