pipeline.merge

Each strategy declares an explicit policy for how branch gates combine. :class:`WeightedSum` and :class:`Mean` AND-combine (conservative): a pair is allowed only when every branch's gate allows it. :class:`Min` and :class:`Max` OR-combine (permissive): a pair is allowed when any branch allows it; this matches the "best-of-branches" reduction semantics. :class:`StackReduce` defaults to AND for user-supplied reducers; pass ``gate_mode="or"`` when the reducer is best-of-branches. Biases always sum additively regardless of mode.