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/skillbar.h

@@ -2,12 +2,16 @@
 
 namespace mods::skillbar {
 
-// Select weapon set / combat-art slot `slot` (0-6) on the taskbar, as its key
-// or a click does.
-void SelectSkillSlot(unsigned slot);
+// Select weapon set `slot` (0-6) on the taskbar, as its key or a click does.
 void SelectWeaponSet(unsigned slot);
 
-// Whether the taskbar shows combat-art slot `slot` (unlocked, control exists).
-bool HasSkillSlot(const void* taskbar, unsigned slot);
+// Make combat-art slot `slot` (0-6) the right mouse button's art. Only skill
+// keys select a slot other than 0, for the duration of their cast; any other
+// selection is turned into slot 0.
+void SelectSkillSlot(unsigned slot);
+unsigned SelectedSkillSlot();
+
+// Whether combat-art slot `slot` is shown (unlocked) and holds an art.
+bool SkillSlotHasArt(unsigned slot);
 
 } // namespace mods::skillbar