Helper to extract a single transfer-entropy-like statistic from a
coefficient table. It looks for columns named "Eff. TE" or
"TE" (in that order) and falls back to the first column if
neither is present.
.get_stat(obj)A numeric scalar with the extracted statistic (first row of
the chosen column), or NA_real_ if extraction fails.
An object produced by RTransferEntropy (or similar) for
which coef(obj) returns a matrix.