Fields that must never enter the feature matrix.
OptionalDenySources that must never be drawn from (optional, in addition to DenyFields).
Importance threshold (e.g. 0.6) above which a single feature's dominance
flags the run as suspicious → warn loudly + block promotion until a human
signs off.
Leakage protection configuration (plan §6.4). An automated feature-search agent will relentlessly exploit target leakage; this guard denies known-leaky fields/sources and flags single-feature dominance for human sign-off.