Summarize posterior snap indices

Usage

snap_index_summary(
  fit,
  actors = NULL,
  years = NULL,
  side = c("u", "v"),
  probs = c(0.025, 0.1, 0.5, 0.9, 0.975)
)

fit: a lame fit with snap-shift MCMC output, or a lame_snap_als fit. MCMC fits should be run with retained snap draws for posterior uncertainty; ALS fits contribute their snap_prob scores as one score row.
actors: optional actor names or indices. Default uses every actor on the selected side.
years: optional year/period names or indices. Default uses every period.
side: "u" for sender/row-side snap indicators or "v" for receiver/column-side indicators.
probs: numeric quantiles to report.

A data frame with one row per selected year.