Apply bootstrap CI to a CL / ED dispatcher fit

The CL and ED workers don't run bootstrap natively. The dispatcher calls this helper to map a bootstrap() summary onto the worker's analytical $full schema – same shape as the in-worker logic in fit_sa(). Premium stays at observed values (loss-only bootstrap; premium-side uncertainty is layered by fit_ratio()).

Usage

.lossfit_bootstrap(
  fit,
  triangle,
  bootstrap,
  B,
  seed,
  alpha,
  conf_level,
  target = "loss"
)