feat(currency): copper/silver/gold replace the coin

The three denominations are move tokens, not stored buckets — there is one
integer, so change-making never arises. The deserter is down to 47c: under a
silver, so he cannot cover a bed and the player sees it on turn one.

A parity test guards the code-side ratios against the content-side ids.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QYa9u7Kdxv5gX4AnwWexy8

client/scripts/newgame/new_game.gd

@@ -61,9 +61,10 @@ static func construct(origin: Dictionary, world: ContentDB, creation: Dictionary
 		var qd: Dictionary = world.quest(quest_id)
 		log.active_quests.append(Quest.new(qd.get("id", ""), qd.get("name", ""), "active", qd.get("objective", "")))
 
-	# inventory grants -> game state (NOT the log). Charter §2.
+	# inventory grants -> game state (NOT the log). Charter §2. grant() routes
+	# currency to the purse; everything else to the inventory dict.
 	for grant in origin.get("inventory_grants", []):
-		state.add_item(grant.get("item_id", ""), int(grant.get("qty", 0)))
+		state.grant(grant.get("item_id", ""), int(grant.get("qty", 0)))
 
 	return {"ok": true, "errors": [], "log": log, "state": state}