feat: 资质概率按难度配置化，新增普通/困难两档权重

- game_config.cfg 新增 difficulty 档位与 [recruitment_normal]/[recruitment_hard] 权重表
- GameConfig 解析各档权重，get_aptitude_weights() 按当前难度返回
- DiscipleManager 资质判定改读配置权重，删除代码常量
- 设计文档补充配置写法说明（VariantParser 数组字面量陷阱）
- 计划表同步 D3 进度

src/Core/GameConfig.gd

@@ -7,6 +7,8 @@ extends Node
 const CONFIG_PATH := "res://resources/game_config.cfg"
 
 # —— 招募系统（对应 cfg 的 [recruitment] 节）——
+## 当前难度档位（对应下方各难度节，如 "normal"/"hard"）。
+var difficulty := "normal"
 ## 开局候选人数。
 var opening_applicant_count := 5
 ## 开局必须选满数。
@@ -16,6 +18,12 @@ var recruit_interval_years := 0.1
 ## 定期弹窗候选人数。
 var recruit_applicant_count := 3
 
+## 各难度资质权重表（键 = 难度档位，值 = 下品/中品/上品/天骄 权重）。
+var aptitude_weights_by_difficulty: Dictionary = {
+	"normal": [45, 35, 15, 5],
+	"hard": [60, 30, 8, 2],
+}
+
 
 func _ready() -> void:
 	_load_config()
@@ -23,10 +31,28 @@ func _ready() -> void:
 ## 读取配置文件；缺失的项保持代码默认值，不会报错。
 func _load_config() -> void:
 	var cfg := ConfigFile.new()
-	if cfg.load(CONFIG_PATH) != OK:
+	var err := cfg.load(CONFIG_PATH)
+	if err != OK:
 		push_warning("GameConfig: 配置文件不存在，使用默认值")
 		return
+	difficulty = cfg.get_value("recruitment", "difficulty", difficulty)
 	opening_applicant_count = cfg.get_value("recruitment", "opening_applicant_count", opening_applicant_count)
 	opening_pick_count = cfg.get_value("recruitment", "opening_pick_count", opening_pick_count)
 	recruit_interval_years = cfg.get_value("recruitment", "recruit_interval_years", recruit_interval_years)
 	recruit_applicant_count = cfg.get_value("recruitment", "recruit_applicant_count", recruit_applicant_count)
+	# 逐档读取难度权重（INI 数组字面量，如 [45, 35, 15, 5]）
+	for key in aptitude_weights_by_difficulty.keys():
+		var raw: Variant = cfg.get_value("recruitment_" + key, "aptitude_weights", [])
+		if raw is Array and raw.size() > 0:
+			var arr: Array[int] = []
+			for w in raw:
+				arr.append(int(w))
+			aptitude_weights_by_difficulty[key] = arr
+
+## 当前难度下的资质权重（下品/中品/上品/天骄）。
+func get_aptitude_weights() -> Array[int]:
+	var raw: Array = aptitude_weights_by_difficulty.get(difficulty, aptitude_weights_by_difficulty["normal"])
+	var result: Array[int] = []
+	for w in raw:
+		result.append(int(w))
+	return result