Combos: cooldown labels on the skill bar, steps follow the arts' current levels

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

docs/combos.md

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+# Combos
+
+## Request (2026-10-18)
+
+Combos don't show their cooldown like other skills. Combos should reference
+the skills they are built from and always use those skills' current levels.
+
+## Measured / read
+
+- Combos live in a vector of 0x26-byte entries at cCreatureArts +0x10e /
+  +0x112, at most 4 (`cCreatureArts::FindCombo` 0x5819a0). Layout in
+  `src/game/engine/arts.h`: id (0x200..0x204), 4 step arts, 4 step levels,
+  total, charge rate, charge.
+- `cCreatureArts::SetCombo` (0x581290, thiscall `(index, arts[4], levels[4],
+  id)`, ret 0x10) fills an entry and computes the total from the levels; the
+  charge starts at 0. The Kombomeister calls it when a combo is made and the
+  levels are never updated afterwards.
+- The charge counts up to the total at the charge rate (recomputed while
+  charging); ready when charge >= total (`IsComboReady` 0x581920).
+- A taskbar slot of type 4 holds combo 0x200 + index.
+- Logged 2026-10-18: a combo made with an art at level 3 stores 3; after the
+  art rose to 4 the mod re-set it to 4 and the total followed.
+
+## Mod
+
+- `skillbar.cpp`: combo slots get the seconds label like other arts,
+  `game::GetComboCooldown` = (total - charge) / rate.
+- `combos.cpp`: every engine tick, the hero's combos are compared with the
+  arts' current levels (cooldown entry level + bonus levels). Out of date →
+  `SetCombo` again with the current levels; the charge keeps its fraction of
+  the total. Skipped while a combo is executing.
+
+## Open
+
+- Whether the Kombomeister stores base or base + item bonus levels is not
+  measured (no art with bonus levels in the test). The mod uses base + bonus;
+  if the cast also adds the bonus it would count twice.