Cross-country contagion features: wins on the tail, regresses on EG. Held back.

We added 3 neighbor-risk features to v3.1 and retrained as v3.2. Stratified F1 jumped 0.673 → 0.712 and the targeted weak countries (PK, TH, SG) improved 3-9 points. But EG regressed 13.5 points and Western Europe got worse too. Net LOCO neutral. Holding v3.2 back; iterating the adjacency map.