feat(client): Luck (deterministic gen/drift/descriptor) + GameState store

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/scripts/state/game_state.gd

@@ -0,0 +1,31 @@
+class_name GameState
+extends RefCounted
+## Luck-centric game state (spec decision 5). The SOLE home of numeric Luck,
+## stats, world-NPC dispositions, and inventory — none of which enter the canon
+## log (charter §7/§2). The log reads only luck_descriptor() from here.
+
+var luck: int = 0
+var luck_base: int = 0
+var stats: Dictionary = {}            # {str, dex, con, fth, mag}
+var npc_dispositions: Dictionary = {} # world-npc id -> int (−100..100)
+var inventory: Dictionary = {}        # item_id -> qty
+
+
+func set_luck(v: int) -> void:
+	luck = clampi(v, Luck.MIN, Luck.MAX)
+
+
+func drift_luck(delta: int) -> void:
+	luck = Luck.drift(luck, luck_base, delta)
+
+
+func luck_descriptor() -> String:
+	return Luck.descriptor(luck)
+
+
+func set_npc_disposition(id: String, v: int) -> void:
+	npc_dispositions[id] = clampi(v, -100, 100)
+
+
+func add_item(item_id: String, qty: int) -> void:
+	inventory[item_id] = int(inventory.get(item_id, 0)) + qty