Shared chest tabs, rune stacks and rune master, Q pickup, Kettenblitz tooltip and range

- Shared chest: tabs "Truhe"/"Gemeinsam" as a column left of the grid
  (game tab sheet), grids placed every tick, persistent across heroes
- Inventory tab texts capitalized (RegisterText / CapitalizeText)
- Combat-art runes stack like potions (itemstack, renamed from potionstack)
- Rune master: any rune for any number of runes, price by rune count
  (4 runes = 1,000, x10 per missing rune), bought rune goes into the
  backpack, Buy disabled without runes, gold or room, last rune remembered
  per hero (saved), the chosen rune's name below its icon, dropping a
  stack gives up one rune
- Keys: the old key handling no longer takes over after the save screen
  (text field focus only counts while its dialog is shown)
- Esc crash: tooltips forgotten when the game destroys them
- Pick up (Q) sends the pickup order directly; search reach doubled
- Kettenblitz: tooltip shows hits per chain, chains, cast and jump range;
  cast range 900 (longer ray segments), jumps half of that

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

src/mods/itemstack.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <cstdint>
+
+namespace mods::itemstack {
+
+// Items of one type in the stack held by item `id` (1 for an item without one).
+unsigned StackCount(uint32_t id);
+
+// Sets the stack size of item `id` (1 or less: no stack). Used when loading.
+void SetStackCount(uint32_t id, unsigned count);
+
+// cInventoryEntry::ReplaceItemId: the stack follows its item to the new id.
+void OnItemIdReplaced(uint32_t oldId, uint32_t newId);
+
+// An item of `type` in `inventory` whose stack has room for one more, or 0.
+uint32_t StackWithRoom(const uint8_t* inventory, uint32_t type);
+
+// Forgets all stacks (a save game is about to be loaded).
+void ResetStacks();
+
+} // namespace mods::itemstack