Sx_persist_store services every persist/* IO op against on-disk storage
(append-only log + separate monotonic .seq high-water + per-key kv files,
SX-serialized). Wired into the (eval) suspension loop, cek_run_with_io
bridge, and in-process _cek_io_resolver. Data-loss repro now (3 3 3).
New persist_durable_test.sh: durable + monotonic-seq + streams + kv +
real process restart all green (5/5).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>