chore(game-ui): extract GameScreen domains

- Extracted `GameScreen` functionality into dedicated UI domains
- Added new panels:
  - `action_bar_panel`
  - `combat_ui`
  - `social_panel`
  - `window_manager`
- Updated `game_screen` + CMakeLists.txt integration
- Added new headers and sources under ui and ui

include/ui/action_bar_panel.hpp

@@ -0,0 +1,78 @@
+// ============================================================
+// ActionBarPanel — extracted from GameScreen
+// Owns all action bar rendering: main bar, stance bar, bag bar,
+// XP bar, reputation bar, macro resolution.
+// ============================================================
+#pragma once
+#include <cstdint>
+#include <unordered_map>
+#include <functional>
+#include <vulkan/vulkan.h>
+
+namespace wowee {
+namespace game { class GameHandler; }
+namespace pipeline { class AssetManager; }
+namespace ui {
+
+class ChatPanel;
+class SettingsPanel;
+class InventoryScreen;
+class SpellbookScreen;
+class QuestLogScreen;
+
+class ActionBarPanel {
+public:
+    // Callback type for resolving spell icons (spellId, assetMgr) → VkDescriptorSet
+    using SpellIconFn = std::function<VkDescriptorSet(uint32_t, pipeline::AssetManager*)>;
+
+    // ---- Action bar render methods ----
+    void renderActionBar(game::GameHandler& gameHandler,
+                         SettingsPanel& settingsPanel,
+                         ChatPanel& chatPanel,
+                         InventoryScreen& inventoryScreen,
+                         SpellbookScreen& spellbookScreen,
+                         QuestLogScreen& questLogScreen,
+                         SpellIconFn getSpellIcon);
+    void renderStanceBar(game::GameHandler& gameHandler,
+                         SettingsPanel& settingsPanel,
+                         SpellbookScreen& spellbookScreen,
+                         SpellIconFn getSpellIcon);
+    void renderBagBar(game::GameHandler& gameHandler,
+                      SettingsPanel& settingsPanel,
+                      InventoryScreen& inventoryScreen);
+    void renderXpBar(game::GameHandler& gameHandler,
+                     SettingsPanel& settingsPanel);
+    void renderRepBar(game::GameHandler& gameHandler,
+                      SettingsPanel& settingsPanel);
+
+    // ---- State owned by this panel ----
+
+    // Action bar error-flash: spellId → wall-clock time (seconds) when the flash ends
+    std::unordered_map<uint32_t, float> actionFlashEndTimes_;
+    static constexpr float kActionFlashDuration = 0.5f;
+
+    // Action bar drag state (-1 = not dragging)
+    int actionBarDragSlot_ = -1;
+    VkDescriptorSet actionBarDragIcon_ = VK_NULL_HANDLE;
+
+    // Bag bar state
+    VkDescriptorSet backpackIconTexture_ = VK_NULL_HANDLE;
+    VkDescriptorSet emptyBagSlotTexture_ = VK_NULL_HANDLE;
+    int bagBarPickedSlot_ = -1;
+    int bagBarDragSource_ = -1;
+
+    // Macro editor popup state
+    uint32_t macroEditorId_   = 0;
+    bool     macroEditorOpen_ = false;
+    char     macroEditorBuf_[256] = {};
+
+    // Macro cooldown cache: maps macro ID → resolved primary spell ID
+    std::unordered_map<uint32_t, uint32_t> macroPrimarySpellCache_;
+    size_t macroCacheSpellCount_ = 0;
+
+private:
+    uint32_t resolveMacroPrimarySpellId(uint32_t macroId, game::GameHandler& gameHandler);
+};
+
+} // namespace ui
+} // namespace wowee