The /new and /reset commands were not calling shutdown_memory_provider()
on the cached agent before eviction. This caused OpenViking (and any
memory provider that relies on session-end shutdown) to skip commit,
leaving memories un-indexed until idle timeout or gateway shutdown.
Add the missing shutdown_memory_provider() call in _handle_reset_command(),
matching the behavior already present in the session expiry watcher.
Fixes#7759
e964cfc403