Compact summary of a df_forest() result. Printing it shows the same
header as print.forest_stats(), then one line per metric with its draw
count n and each covariate's levels in plot order. A covariate whose
level repeats its name (the reference panel) shows the name alone;
reference copies drawn in a covariate panel are marked *.
Value
A summary.forest_stats object (also summary.pmx_stats): a list
with header (the class tag, dim of stats, obs_rows, and the
config values shown by print.forest_stats()), metrics (a
data.frame with one row per metric and columns metric, n_min and
n_max (the range of n, NA when stats has no n column), and
panels, the covariate panels and levels in plot order as printed), and
has_distributed (whether any reference copy sits in a covariate
panel).
