6cd1ed2e78
test_flat_key_wins_over_subblock asserted the OPPOSITE of its name (the sub-block wins, matching _relay_slack_extra). Rename to what it proves. Also note in _resolve_cron_surface_mode why its fallback differs from _relay_slack_extra's all-or-nothing sub-dict: the flat key is the legacy staging shape, and a flat knob applies to every fronted platform, gated only by the per-platform D6 capability check.