Adds a dnd_zone_run.harvest_nodes_json column and a small persistence
layer (loadStandaloneHarvestNodes / saveStandaloneHarvestNodes) so
!zone enter runs that aren't tied to an expedition can carry per-room
HarvestNode state. Expedition runs continue to use
expedition.region_state for the same data — this is the casual flow.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
