Skills, auto-attack, aura and chain lightning rework, Esc, cache fix

- Skill bar: no art selection; slot 0 is the right-click art, keys 0-6 cast
  slots directly; cooldown labels in exact seconds; slot 0 set apart.
- Arts regenerate on their own (casting no longer refills the group).
- Auto-attack after targeting or casting at a hostile creature, at the speed
  of a held button.
- Auras can be recast while active (renew, no second visual).
- Blicke wie Klingen hits every enemy in range, physical, with life leech.
- Blitzschlag steers the game's own chain: 3 + level/5 hits, 1 + level/10
  chains, re-hits a lone enemy.
- Weapon sets: click selects, drag only from the selected set; the leftmost
  set is clickable (signed hit tests).
- Esc closes open windows before opening the game menu.
- HUD: standalone buttons and texts are centred.
- Record cache sized for widened views (town lag while walking).
- Shared game code: orders, fx events, text drawing, cooldowns, effects.

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

src/mods/skillslots.cpp

@@ -45,6 +45,11 @@ int IndexOf(const void* inventory) {
 
 } // namespace
 
+uint8_t* Inventory(unsigned index) {
+    auto* base = *reinterpret_cast<uint8_t**>(kInventoryBlock);
+    return base && index < kInventories ? base + index * kInventorySize : nullptr;
+}
+
 uint8_t* ShadowFor(const void* inventory, bool create) {
     const int index = IndexOf(inventory);
     if (index < 0) {