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>

docs/chain-lightning.md

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+# Chain lightning (`src/mods/chainlightning.cpp`)
+
+Rebalancing request (user, 2026-10-15) for the Battlemage's Blitzschlag (art
+0x21, icon `GUI_SPELL_BLITZSCHLAG`; 0x0e has the same icon):
+
+- hits per chain N = 3 + level / 5 (the first target included);
+- chains B = 1 + level / 10, all starting at the first target
+  ("hero -> T1 -> A1 -> A2 ..., T1 -> B1 -> B2 ...");
+- a chain that finds no new target hits the previous one again (a lone enemy
+  takes N hits).
+
+## How the game casts it (measured with an object / hit log, 2026-10-15)
+
+About 0.3 s after the cast order (0x105, art 0x21) the caster's art code
+(`0x5222c0`, Blitzschlag part around `0x526c91`..`0x527102`):
+
+- builds the visual path: up to 20 segment objects of type 799 (0x31f),
+  each created linked to the previous one (`CreateAt` third argument), ids
+  kept at caster +0x263;
+- creates the bolt object, type 872 (0x368), at the target, linked to the
+  last segment, copies the caster's +0x2b5 to its +0x39, and sends it a
+  cEventFX 0x60 (`0x41e0a0`: [2] caster id, [3] target id, [4..7] position,
+  [8..13] two strings, [14] damage, [16..29] damage block);
+- plays sound 0x7db.
+
+The bolt object then sends the hit (`cEvent_creature` 5 from `0x5b52d3`,
+attacker = caster, +0x14 = 0x368, +0x18 = the bolt object's id).
+
+## The game's own chain (measured 2026-10-15)
+
+The game's Blitzschlag already chains. The 0x60 event's [14] is the number of
+hits left in the chain (3 at level 1, from the art level, `0x4d24f0`). After
+its hit, a bolt with hits left looks for the next target in its update
+(`cObjectManager::FindJumpTarget` `0x6005d0`, called at `0x5b469f` with
+(position, 100000 = squared range, caster, current target): the nearest
+creature, excluding only caster and current target), builds the arc (segment
+objects 799 created at `0x5b4aff`, each set up with a cEventFX), and creates
+the next bolt at the target (`0x5b4d7c`) with [14] - 1. No target: the chain
+ends (a lone enemy is hit once). Two enemies: it bounces between them.
+
+## The mod
+
+- The first bolt of a hero's cast (the first 0x60 bolt setup after the cast
+  order) gets [14] = N = 3 + level / 5 (level = cooldown entry level + bonus
+  levels of the art cast).
+- The jump search call (`0x5b469f`) goes to `NextTarget` (thunk passing the
+  bolt in ebp): for bolts of our chains (bolt id -> chain, filled when a bolt
+  of a chain is set up at the target the chain said it jumps to) the next
+  target is the nearest enemy within the game's range not hit by this chain
+  yet, else another enemy, else the current one again (a lone enemy takes all
+  N hits). Other bolts use the game's search.
+- B = 1 + level / 10 chains: while the first bolt is set up, B - 1 more bolts
+  are created at the first jump targets of the other chains (copies of the
+  event with [14] = N - 1); their first hop has no arc.
+
+First version (bolts copied for every jump, not using the game's chain)
+replaced the same day: it doubled the jumps.