Fix vendor buying, improve character select, parallelize WMO culling, and optimize collision

- Fix CMSG_BUY_ITEM count field from uint8 to uint32 (server silently dropped undersized packets)
- Character select screen: remember last selected character, two-column layout with details panel, double-click to enter world, responsive window sizing
- Fix stale character data between logins by replacing static init flag with per-character GUID tracking
- Parallelize WMO visibility culling across worker threads (same pattern as M2 renderer)
- Optimize WMO collision queries with world-space group bounds early rejection in getFloorHeight, checkWallCollision, isInsideWMO, and raycastBoundingBoxes
- Reduce camera ground samples from 5 to 3 movement-aligned probes
- Add WMO interior lighting, unlit materials, vertex color multiply, and alpha blending support

include/game/game_handler.hpp

@@ -324,6 +324,10 @@ public:
     const std::array<ActionBarSlot, ACTION_BAR_SLOTS>& getActionBar() const { return actionBar; }
     void setActionBarSlot(int slot, ActionBarSlot::Type type, uint32_t id);
 
+    void saveCharacterConfig();
+    void loadCharacterConfig();
+    static std::string getCharacterConfigDir();
+
     // Auras
     const std::vector<AuraSlot>& getPlayerAuras() const { return playerAuras; }
     const std::vector<AuraSlot>& getTargetAuras() const { return targetAuras; }
@@ -449,7 +453,7 @@ public:
     // Vendor
     void openVendor(uint64_t npcGuid);
     void closeVendor();
-    void buyItem(uint64_t vendorGuid, uint32_t itemId, uint32_t slot, uint8_t count);
+    void buyItem(uint64_t vendorGuid, uint32_t itemId, uint32_t slot, uint32_t count);
     void sellItem(uint64_t vendorGuid, uint64_t itemGuid, uint32_t count);
     void sellItemBySlot(int backpackIndex);
     void autoEquipItemBySlot(int backpackIndex);

include/game/world_packets.hpp

@@ -1637,7 +1637,7 @@ public:
 /** CMSG_BUY_ITEM packet builder */
 class BuyItemPacket {
 public:
-    static network::Packet build(uint64_t vendorGuid, uint32_t itemId, uint32_t slot, uint8_t count);
+    static network::Packet build(uint64_t vendorGuid, uint32_t itemId, uint32_t slot, uint32_t count);
 };
 
 /** CMSG_SELL_ITEM packet builder */

include/rendering/wmo_renderer.hpp

@@ -245,6 +245,8 @@ private:
         glm::vec3 boundingBoxMin;
         glm::vec3 boundingBoxMax;
 
+        uint32_t groupFlags = 0;
+
         // Material batches (start index, count, material ID)
         struct Batch {
             uint32_t startIndex;   // First index in EBO
@@ -258,6 +260,8 @@ private:
             GLuint texId;
             bool hasTexture;
             bool alphaTest;
+            bool unlit = false;
+            uint32_t blendMode = 0;
             std::vector<GLsizei> counts;
             std::vector<const void*> offsets;
         };
@@ -302,6 +306,9 @@ private:
         // Material blend modes (materialId -> blendMode; 1 = alpha-test cutout)
         std::vector<uint32_t> materialBlendModes;
 
+        // Material flags (materialId -> flags; 0x01 = unlit)
+        std::vector<uint32_t> materialFlags;
+
         // Portal visibility data
         std::vector<PortalData> portals;
         std::vector<glm::vec3> portalVertices;
@@ -339,7 +346,7 @@ private:
     /**
      * Create GPU resources for a WMO group
      */
-    bool createGroupResources(const pipeline::WMOGroup& group, GroupResources& resources);
+    bool createGroupResources(const pipeline::WMOGroup& group, GroupResources& resources, uint32_t groupFlags = 0);
 
     /**
      * Render a single group
@@ -492,6 +499,17 @@ private:
     mutable std::vector<size_t> candidateScratch;
     mutable std::unordered_set<uint32_t> candidateIdScratch;
 
+    // Parallel visibility culling
+    uint32_t numCullThreads_ = 1;
+
+    struct InstanceDrawList {
+        size_t instanceIndex;
+        std::vector<uint32_t> visibleGroups;  // group indices that passed culling
+        uint32_t portalCulled = 0;
+        uint32_t distanceCulled = 0;
+        uint32_t occlusionCulled = 0;
+    };
+
     // Collision query profiling (per frame).
     mutable double queryTimeMs = 0.0;
     mutable uint32_t queryCallCount = 0;

include/ui/character_screen.hpp

@@ -54,6 +54,7 @@ private:
     int selectedCharacterIndex = -1;
     bool characterSelected = false;
     uint64_t selectedCharacterGuid = 0;
+    bool restoredLastCharacter = false;
 
     // Status
     std::string statusMessage;
@@ -69,6 +70,13 @@ private:
      * Get faction color based on race
      */
     ImVec4 getFactionColor(game::Race race) const;
+
+    /**
+     * Persist / restore last selected character GUID
+     */
+    static std::string getConfigDir();
+    void saveLastCharacter(uint64_t guid);
+    uint64_t loadLastCharacter();
 };
 
 }} // namespace wowee::ui

include/ui/game_screen.hpp

@@ -37,6 +37,9 @@ public:
      */
     bool isChatInputActive() const { return chatInputActive; }
 
+    void saveSettings();
+    void loadSettings();
+
 private:
     // Chat state
     char chatInputBuffer[512] = "";
@@ -66,10 +69,10 @@ private:
     int pendingSfxVolume = 100;
     float pendingMouseSensitivity = 0.2f;
     bool pendingInvertMouse = false;
-    int pendingUiOpacity = 100;
+    int pendingUiOpacity = 65;
 
     // UI element transparency (0.0 = fully transparent, 1.0 = fully opaque)
-    float uiOpacity_ = 1.0f;
+    float uiOpacity_ = 0.65f;
 
     /**
      * Render player info window
@@ -152,6 +155,7 @@ private:
     void renderWorldMap(game::GameHandler& gameHandler);
 
     InventoryScreen inventoryScreen;
+    uint64_t inventoryScreenCharGuid_ = 0;  // GUID of character inventory screen was initialized for
     QuestLogScreen questLogScreen;
     SpellbookScreen spellbookScreen;
     TalentScreen talentScreen;
@@ -174,6 +178,8 @@ private:
     int actionBarDragSlot_ = -1;
     GLuint actionBarDragIcon_ = 0;
 
+    static std::string getSettingsPath();
+
     // Left-click targeting: distinguish click from camera drag
     glm::vec2 leftClickPressPos_ = glm::vec2(0.0f);
     bool leftClickWasPress_ = false;