feat: authoritative extraction from ResourceNode on task completion

Phase 3 of ResourceNode migration:
- Add apply_resource_delta to SimVillage for clean resource changes
- Extract from reserved ResourceNode on task completion instead of
  hard-coded apply_npc_task for gather_food/gather_wood
- Detect depleted/unavailable targets on arrival and replan

simulation/SimVillage.gd

@@ -69,6 +69,25 @@ func update_priorities() -> void:
 	if DEBUG_LOGS:
 		print(get_priority_summary())
 
+func apply_resource_delta(resource_id: StringName, amount: float) -> void:
+	match resource_id:
+		&"food":
+			food += amount
+		&"wood":
+			wood += amount
+		&"safety":
+			safety = clamp(safety + amount, 0.0, 100.0)
+		&"knowledge":
+			knowledge += amount
+
+	food = max(food, 0.0)
+	wood = max(wood, 0.0)
+	safety = clamp(safety, 0.0, 100.0)
+	knowledge = max(knowledge, 0.0)
+
+	update_modifiers()
+	update_priorities()
+
 func apply_npc_task(npc: SimNPC) -> void:
 	if npc.is_dead:
 		return