Add resource node persistence

Docs/Terrain/GroundZeroResourcePass.md

@@ -69,6 +69,15 @@ immediate benefit:
 The rule is inventory-based until equipment slots, durability, and explicit
 active-hand state are implemented.
 
+## Persistence
+
+Ground Zero resource actors receive stable `PersistenceNodeId` values matching
+their placement labels. The persistence subsystem captures and restores only
+resource nodes that exist in the loaded world, so depletion records stay scoped
+to active map/tile content. Future generated Earth-scale tiles should follow the
+same rule: assign deterministic resource node IDs during placement and let the
+save system record depletion only for tiles whose resource actors are present.
+
 ## Follow-Up
 
 Future passes should replace the prototype meshes with real coastal scrub,