sketch_cb_vs_cuckoo_delete_bench.nx

sketch_cb_vs_cuckoo_delete_bench.nx -- both-support-delete paired bench. CLAIM TO VALIDATE: Counting Bloom (Fan-Cao-Almeida-Broder 1998) supports DELETE via per-counter decrement. Cuckoo (Fan-Andersen-Kaminsky-Mitzenmacher 2014) also supports DELETE via fingerprint clear. Substrate ships both. Different trade-offs: - Counting Bloom: per-counter byte (8x more memory than Bloom) but multi-set multiplicity tracking. - Cuckoo: 1-byte fingerprint per slot, tighter FPR per byte. Bench measures: at MATCHED memory, both correctly forget deleted items (within FPR bounds); Cuckoo's FPR is tighter at typical load. WORKLOAD: Insert 500 distinct keys into both. Delete first 100. Verify >=90% of deleted keys correctly forgotten by EACH (capability axis = both pass). Compare FPR post-delete on a 1000-key disjoint test set (accuracy axis = Cuckoo's tighter wins).