Extend the end-to-end harness (issue #15), harness-only — no server change:
Combat validation
- replayed/out-of-order combat sequence rejected and not routed
- combat hit at a disconnected target rejected
- out-of-interest combat hit rejected and not delivered
NPC authority handoff
- disconnect deterministically hands off to a new owner with a newer epoch
- cell transition hands off scope authority and the previous owner can no longer
submit npcState for the reassigned scope
21/21 pass on real sockets, deterministic across repeated runs.
