Refits the model with fishing mortality set to 0 from styr on, keeping
every other parameter. The projection after endyr is always unfished.
run_mse() uses it for the no-fishing run (OM_no_F) behind the collapse
metrics.
Details
styr may be any year from the model's own styr to endyr + 1; the
projection is unfished whatever harvest control rule the model was fit under.
Under predation, empirical suitability (suitMode = 0) is derived from the
fitted abundance over each predator's suit_styr:suit_endyr, so styr must
fall after that window for every predator with suitMode = 0 and diet data
in it.