Make cross-domain couplings emergent via one observer-relative primitive, not per-case filters

When a simulation needs economics to depend on politics/relationships, the tempting fix is a special-case filter like exclude-if-enemy. That is the anti-pattern: a rule named after its outcome. The emergent fix is to make the value read OBSERVER-RELATIVE and route it through a primitive that already encodes the relationship, e.g. transactability(seller,buyer) = a monotone read of the relation sentiment weight, then weight demand by it. Then both you-cannot-sell-to-an-enemy and an-ally-deepens-your-market fall out of one function with no friend/foe table, and the SAME primitive is reusable for every coupling since it is the pairwise case of a coalition value function counterparties term. Keep it opt-in behind a meta flag so the off-path stays byte-identical.