Background copy-on-write GOBLIN.SAVE, two crash fixes (member-arena and
score-index overflows), and a rigorous 4-engine memory-first benchmark (vs Redis
7.2.4, Redis 8.8, Valkey 9.1 under jemalloc 5.3.0 + config parity): ~49 B/member,
roughly half the RAM of the leanest competitor. Throughput deferred to a quiet
host (benchmark VM too noisy).