User folders: save games and Settings.cfg in Documents\Sacred

The game's ANSI file API calls are hooked; paths under save\ and
Settings.cfg are redirected to Documents\Sacred\save and
Documents\Sacred\config, copied there once from the game folder.
The shared chest uses the same save folder.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/shared-chest.md

@@ -4,7 +4,8 @@
 
 The chest gets a second tab that belongs to no single hero: a chest shared by
 all characters. Decided: stored in one file in the save folder
-(`save\shared_chest.json`), two tabs ("Truhe" / "Gemeinsam"), same size as the
+(`shared_chest.json` in the save folder, `Documents\Sacred\save`, see
+`user-folders.md`), two tabs ("Truhe" / "Gemeinsam"), same size as the
 chest (20 x 10). Potions stack in it like in every player inventory
 (docs/item-stacks.md). Follow-up (same day): text tabs were barely visible;
 use the inventory's Rucksack / Kampfkünste / Combos header look with its