Collects the per-task rank__by_param entries (from
rank_metric()) into a long tibble with columns task_id, param,
rank, n_draws, plus atomic data_* and fit_* condition columns.
Returns an empty tibble if no rank metric was computed.
Examples
if (FALSE) { # \dontrun{
result <- run_simulation(config, progress = FALSE)
ranks <- sbc_ranks(result)
} # }