feat: FOG stress ablation with new tasks (conditional, intersection, compose_add, multihop)

sync: FOG micro+medium configs, stress tasks, fast pipeline

fix: recognize uniform_small model type in run_experiment

fix: proper controls — loss masking, uniform baseline, multi-seed

fix: add tiny config (seq=32, d=128) for fast FOG ablation

feat: add FOG ablation framework for motif-aware transformer experiments