Character panel: minus buttons take back attribute and skill points

- respec: the panel's unused second button array becomes − buttons between
  name and value; attributes give back invested points, skills give back
  skill points, a level-1 skill is removed and can be chosen anew; all
  through the game's own point functions (protected copy stays in sync)
- the − is the + icon with its vertical arm covered (no minus image exists)
- hud: RenderCentred / HandleCentred for mods hooking centred windows;
  mouse event helpers shared in game/ui/events.h

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

src/game/ui/events.h

@@ -0,0 +1,30 @@
+#pragma once
+// UI events (cEvent subclasses handed to the windows' vf10).
+
+#include <cstdint>
+
+namespace game {
+
+// Mouse events, by their vf04 category (positions in render pixels):
+//   1 cEvent_mouseMove:          previous x, y at +4 / +8, current at +0xc / +0x10
+//   2 cEvent_mouseButton_down,
+//   3 cEvent_mouseButton_up:     button at +4 (0: left), x, y at +8 / +0xc
+enum class MouseEvent { None = 0, Move = 1, ButtonDown = 2, ButtonUp = 3 };
+
+inline MouseEvent MouseEventKind(void* event) {
+    using CategoryFn = int(__fastcall*)(void* self, void* edx);
+    auto category = reinterpret_cast<CategoryFn>((*static_cast<void***>(event))[1]);
+    const int kind = category(event, nullptr);
+    return kind >= 1 && kind <= 3 ? static_cast<MouseEvent>(kind) : MouseEvent::None;
+}
+
+constexpr size_t kMouseButton = 0x4;
+constexpr size_t kMouseButtonX = 0x8;
+constexpr size_t kMouseButtonY = 0xc;
+constexpr int kLeftButton = 0;
+
+inline int32_t EventField(void* event, size_t offset) {
+    return *reinterpret_cast<int32_t*>(static_cast<uint8_t*>(event) + offset);
+}
+
+} // namespace game