Provides bridge equations with optional autoregressive terms for
nowcasting low-frequency macroeconomic variables (e.g. quarterly GDP) from
higher-frequency indicators (e.g. monthly retail sales). Handles the
ragged-edge problem where different indicators have different publication
lags via mixed-frequency alignment. Includes pseudo-real-time evaluation
with expanding or rolling windows, and the Diebold-Mariano test for
comparing forecast accuracy following Harvey, Leybourne, and Newbold
(1997)