feat(meta): MetaProgress autoload（碎片+已解锁+持久化 user://meta.json）

scripts/autoloads/meta_progress.gd

@@ -0,0 +1,55 @@
+## MetaProgress — 全局元进展（Autoload: MetaProgress）
+## 以太碎片 + 已解锁法术，持久化 user://meta.json（死亡不重置）。
+extends Node
+
+const PATH: String = "user://meta.json"
+
+var aether: int = 0
+var unlocked: Array = []   # 已解锁法术 id (String)
+
+func _ready() -> void:
+	load_meta()
+
+func add_aether(n: int) -> void:
+	if n <= 0:
+		return
+	aether += n
+	save_meta()
+
+func is_unlocked(id: String) -> bool:
+	return id in unlocked
+
+## 已解锁 或 碎片不足 → false（不扣费）；否则扣费+记录+存档 → true
+func unlock(id: String, cost: int) -> bool:
+	if is_unlocked(id) or aether < cost:
+		return false
+	aether -= cost
+	unlocked.append(id)
+	save_meta()
+	return true
+
+func clear() -> void:
+	aether = 0
+	unlocked = []
+	if FileAccess.file_exists(PATH):
+		DirAccess.remove_absolute(ProjectSettings.globalize_path(PATH))
+
+func save_meta() -> void:
+	var f := FileAccess.open(PATH, FileAccess.WRITE)
+	if f:
+		f.store_string(JSON.stringify({"aether": aether, "unlocked": unlocked}))
+		f.close()
+
+func load_meta() -> void:
+	aether = 0
+	unlocked = []
+	if not FileAccess.file_exists(PATH):
+		return
+	var parsed = JSON.parse_string(FileAccess.get_file_as_string(PATH))
+	if not (parsed is Dictionary):
+		return
+	aether = int(parsed.get("aether", 0))
+	var u = parsed.get("unlocked", [])
+	if u is Array:
+		for id in u:
+			unlocked.append(String(id))