The wire protocol required an explicit HELLO acknowledgement frame; a
HELLO-only client would otherwise block on the next recv. Add the ACK.
Ad-hoc E2E (real built cube-server, real 4-byte LE framed Unix socket):
- SHARED mode: a HELLO tenant and a no-HELLO client share ONE store
(write visible across both) — backward-compatible with cubec/stress.sh.
- PER-TENANT mode (--tenant-dir): two HELLO tenants are HARD-isolated
(T2 and default tenant cannot see T1's record).
Verifier: /tmp/hermes-verify-driver.sh + /tmp/hermes-verify-e2e.py
CUBELinux-2
7f18218aca