Refactor save management; enhance save_data function with verification and plaintext copy options, and update load_data logic for improved error handling

autoload/global.gd

@@ -2,6 +2,9 @@ extends Node
 
 const SPEED_LIMIT: int = 5
 
+# Write a readable diagnostic copy next to the encrypted save. Never used for loading.
+var save_plaintext_copy: bool = true
+
 var Settings: Dictionary = {
         "filename": "save-0001",
         "sound_volume": 1.0,
@@ -39,7 +42,7 @@ func get_description(item_id: String, items: Array = []) -> String:
 func format_number(value: float, digits: int = 0) -> String:
     if value == 0: return ""
     if value < 10_000:
-        return "%.*f" % [digits, value] 
+        return "%.*f" % [digits, value]
 
     var exp_value = int(floor(log(abs(value)) / log(10.0)))
     var mantissa = value / pow(10.0, exp_value)