ML: Pruning

Reflected-random-walk expert ecology

Turn a sparse expert layer into a stochastic birth-death population. Each expert receives a bounded fitness score from recent routed-token performance; at each update, a candidate expert is activated with probability p, while one expert is removed with probability q = 1 - p, preferentially removing the lowest-fitness expert. The paper's critical threshold f_c = q/p predicts which fitness levels can maintain a growing surviving population, providing a principled control knob for expert turnover.