nx_procgen_features_test.nx

nx_procgen_features_test.nx -- KATs for the P3 biome-lawed feature kinds. Exit 0 = all pass; first failing KAT's number is the exit code. KAT 1 determinism: same (land, biomes, seed) twice -> identical kinds. KAT 2 validity: every kind is sealed (0..3). KAT 3 histogram conservation: counts sum to n_features. KAT 4 variety axis LIVE: grader FEATURE_VARIETY >= 9830 (WIN floor) worst-of-3-seeds on the mountain preset. KAT 5 variety discriminates: an all-ICE biome map (rock-only law) scores 0; the real map scores strictly higher. KAT 6 biome law holds: a pure-DESERT map grows NO trees. KAT 7 independent streams: kinds seed does not change the biome map. KAT 8 width: every preset x 3 seeds stays >= 6553 (marginal floor) -- the variety axis must never fall back into LOSS territory (honest 2026-06-10 baseline: meadow worst = 6585; forest/meadow rock-band skew is the named P4/P5 improvement surface). license_tier: ORIGINAL