The exact 8-column dd coefficient contract (term, estimate,
std.error, statistic, p.value, component, estimate_scale,
term_display). Estimates are posterior medians and std.error
posterior SDs of the report-space-transformed draws (exact; no delta
method); statistic/p.value are NA – use confint() for interval
summaries. The shape row (s, two-parameter equations) carries
component = "shape"; variance rows (effects = "ran_pars") mirror the
TMB reporting convention (log10-scale k RE SD; natural phi/sigma).
