- Add persist.rs: std-only NDJSON snapshot of the HashBackend store
(no serde) for the durable checkpoint + load_into_store replay.
- Add store.rs: ConcurrentStore = Mutex<HashBackend> live store + WAL
(newline-delimited JSON, group-commit fsync, idempotent seq-numbered
replay) + durable JSON checkpoint + bg flusher + startup replay.
- Recovery events (checkpoint failure, WAL fsync failure, WAL replay)
are written to a recovery.ndjson you asked to keep as the written backup
log, so any fall-back to JSON is recorded 'in writing'.
- Refactor cube-server to thread-per-connection over ConcurrentStore.
- query_doc_type / scan_prefix / linked_to / delete_raw added.
Verified: ./check (fmt, 7 unit tests, clippy -D warnings) all green;
./check stress drove 22,080 prog+run pairs (~368/s) over 60s, daemon
survived, latency prog~9us/run~13us mean.
CUBELinux-2
7ccb29aa6a