nx_procgen_biome_test.nx

nx_procgen_biome_test.nx -- KATs for the P2 causal biome map. Exit 0 = all pass; first failing KAT's number is the exit code. KAT 1 determinism: same (heightmap, seed) twice -> identical maps. KAT 2 validity: every cell holds a sealed biome ID. KAT 3 lawfulness: grader BIOME_COHERENCE >= 12000 on a generated world (the R1 ladder target; lawful-by-construction, grader-proven). KAT 4 moisture works: a different moisture seed changes the map, and one map's MID band holds >= 2 distinct biomes. KAT 5 tamper RED: an all-ICE map scores LOW coherence (< 8000) -- the axis discriminates, it doesn't rubber-stamp. KAT 6 flat-map refusal path: range 0 builds valid biomes, no crash. KAT 7 every preset x 2 seeds: coherence >= 12000 (width, worst-case). KAT 8 elevation band function mirrors the grader's quartile cuts. license_tier: ORIGINAL