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

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+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

client/scripts/state/game_state.gd.uid

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+uid://c0ffensw2ym6w

client/scripts/state/luck.gd

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+class_name Luck
+extends RefCounted
+## Numeric Luck (charter §7). Lives in GameState; only descriptor() reaches the
+## log. Deterministic given a seeded RNG (charter §10). Die/range/bands are
+## TUNABLE constants — not final values.
+
+const MIN := 1
+const MAX := 20
+const DRIFT := 3
+
+const BANDS := [
+	{"max": 4, "text": "Fortune spits on you"},
+	{"max": 8, "text": "The world is not on your side"},
+	{"max": 12, "text": "The dice are indifferent"},
+	{"max": 16, "text": "Luck rides with you"},
+	{"max": 20, "text": "The dice are kind today"},
+]
+
+
+static func roll_base(rng: RandomNumberGenerator, modifier: int) -> int:
+	var total := 0
+	for i in 5:
+		total += rng.randi_range(1, 20)
+	return clampi(roundi(total / 5.0) + modifier, MIN, MAX)
+
+
+static func drift(current: int, base: int, delta: int) -> int:
+	return clampi(clampi(current + delta, base - DRIFT, base + DRIFT), MIN, MAX)
+
+
+static func descriptor(luck: int) -> String:
+	for band in BANDS:
+		if luck <= band["max"]:
+			return band["text"]
+	return BANDS[-1]["text"]

client/scripts/state/luck.gd.uid

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+uid://dah05dv3uoym