Directionality

Return the per-pair directionality labels for peg_type.

Productizes the asymmetric conditionals the empirical estimator emits: per pair, asymmetry = conditional_ab − conditional_ba and a first-class direction label (a_drives_b / b_drives_a / symmetric). Reads the latest run's frozen pair_directionality rows (written by the slow-cycle calibration pass), strongest directional claims first (directed pairs by confidence desc), wrapped in the same provenance envelope as /pairwise plus the §6 directionality disclaimer. Sub-floor pairs carry direction='insufficient_support' — reported, never asserted. Pre-calibration (no run / no rows) returns an empty set with a null envelope.