feat: add item stack splitting via Shift+right-click

Implements CMSG_SPLIT_ITEM (0x10E) with a slider popup for choosing
split count. Auto-finds empty destination slot across backpack and bags.
Shift+right-click on stackable items (count > 1) opens split dialog;
non-stackable items still get the destroy confirmation.

include/game/game_handler.hpp

@@ -2029,6 +2029,7 @@ public:
     void openItemBySlot(int backpackIndex);
     void openItemInBag(int bagIndex, int slotIndex);
     void destroyItem(uint8_t bag, uint8_t slot, uint8_t count = 1);
+    void splitItem(uint8_t srcBag, uint8_t srcSlot, uint8_t count);
     void swapContainerItems(uint8_t srcBag, uint8_t srcSlot, uint8_t dstBag, uint8_t dstSlot);
     void swapBagSlots(int srcBagIndex, int dstBagIndex);
     void useItemById(uint32_t itemId);

include/game/world_packets.hpp

@@ -2046,6 +2046,13 @@ public:
     static network::Packet build(uint8_t dstBag, uint8_t dstSlot, uint8_t srcBag, uint8_t srcSlot);
 };
 
+/** CMSG_SPLIT_ITEM packet builder */
+class SplitItemPacket {
+public:
+    static network::Packet build(uint8_t srcBag, uint8_t srcSlot,
+                                 uint8_t dstBag, uint8_t dstSlot, uint8_t count);
+};
+
 /** CMSG_SWAP_INV_ITEM packet builder */
 class SwapInvItemPacket {
 public:

include/ui/inventory_screen.hpp

@@ -187,6 +187,14 @@ private:
     uint8_t destroyCount_ = 1;
     std::string destroyItemName_;
 
+    // Stack split popup state
+    bool splitConfirmOpen_ = false;
+    uint8_t splitBag_ = 0xFF;
+    uint8_t splitSlot_ = 0;
+    int splitMax_ = 1;
+    int splitCount_ = 1;
+    std::string splitItemName_;
+
     // Pending chat item link from shift-click
     std::string pendingChatItemLink_;
 

src/game/game_handler.cpp

@@ -21177,6 +21177,40 @@ void GameHandler::destroyItem(uint8_t bag, uint8_t slot, uint8_t count) {
     socket->send(packet);
 }
 
+void GameHandler::splitItem(uint8_t srcBag, uint8_t srcSlot, uint8_t count) {
+    if (state != WorldState::IN_WORLD || !socket) return;
+    if (count == 0) return;
+
+    // Find a free slot for the split destination: try backpack first, then bags
+    int freeBp = inventory.findFreeBackpackSlot();
+    if (freeBp >= 0) {
+        uint8_t dstBag = 0xFF;
+        uint8_t dstSlot = static_cast<uint8_t>(23 + freeBp);
+        LOG_INFO("splitItem: src(bag=", (int)srcBag, " slot=", (int)srcSlot,
+                 ") count=", (int)count, " -> dst(bag=0xFF slot=", (int)dstSlot, ")");
+        auto packet = SplitItemPacket::build(srcBag, srcSlot, dstBag, dstSlot, count);
+        socket->send(packet);
+        return;
+    }
+    // Try equipped bags
+    for (int b = 0; b < inventory.NUM_BAG_SLOTS; b++) {
+        int bagSize = inventory.getBagSize(b);
+        for (int s = 0; s < bagSize; s++) {
+            if (inventory.getBagSlot(b, s).empty()) {
+                uint8_t dstBag = static_cast<uint8_t>(19 + b);
+                uint8_t dstSlot = static_cast<uint8_t>(s);
+                LOG_INFO("splitItem: src(bag=", (int)srcBag, " slot=", (int)srcSlot,
+                         ") count=", (int)count, " -> dst(bag=", (int)dstBag,
+                         " slot=", (int)dstSlot, ")");
+                auto packet = SplitItemPacket::build(srcBag, srcSlot, dstBag, dstSlot, count);
+                socket->send(packet);
+                return;
+            }
+        }
+    }
+    addSystemChatMessage("Cannot split: no free inventory slots.");
+}
+
 void GameHandler::useItemBySlot(int backpackIndex) {
     if (backpackIndex < 0 || backpackIndex >= inventory.getBackpackSize()) return;
     const auto& slot = inventory.getBackpackSlot(backpackIndex);

src/game/world_packets.cpp

@@ -4358,6 +4358,17 @@ network::Packet SwapItemPacket::build(uint8_t dstBag, uint8_t dstSlot, uint8_t s
     return packet;
 }
 
+network::Packet SplitItemPacket::build(uint8_t srcBag, uint8_t srcSlot,
+                                       uint8_t dstBag, uint8_t dstSlot, uint8_t count) {
+    network::Packet packet(wireOpcode(Opcode::CMSG_SPLIT_ITEM));
+    packet.writeUInt8(srcBag);
+    packet.writeUInt8(srcSlot);
+    packet.writeUInt8(dstBag);
+    packet.writeUInt8(dstSlot);
+    packet.writeUInt8(count);
+    return packet;
+}
+
 network::Packet SwapInvItemPacket::build(uint8_t srcSlot, uint8_t dstSlot) {
     network::Packet packet(wireOpcode(Opcode::CMSG_SWAP_INV_ITEM));
     packet.writeUInt8(srcSlot);

src/ui/inventory_screen.cpp

@@ -871,6 +871,35 @@ void InventoryScreen::render(game::Inventory& inventory, uint64_t moneyCopper) {
         ImGui::EndPopup();
     }
 
+    // Stack split popup
+    if (splitConfirmOpen_) {
+        ImVec2 mousePos = ImGui::GetIO().MousePos;
+        ImGui::SetNextWindowPos(ImVec2(mousePos.x - 80.0f, mousePos.y - 20.0f), ImGuiCond_Always);
+        ImGui::OpenPopup("##SplitStack");
+        splitConfirmOpen_ = false;
+    }
+    if (ImGui::BeginPopup("##SplitStack", ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoTitleBar)) {
+        ImGui::Text("Split %s", splitItemName_.c_str());
+        ImGui::Spacing();
+        ImGui::SetNextItemWidth(120.0f);
+        ImGui::SliderInt("##splitcount", &splitCount_, 1, splitMax_ - 1);
+        ImGui::Spacing();
+        if (ImGui::Button("OK", ImVec2(55, 0))) {
+            if (gameHandler_ && splitCount_ > 0 && splitCount_ < splitMax_) {
+                gameHandler_->splitItem(splitBag_, splitSlot_, static_cast<uint8_t>(splitCount_));
+            }
+            splitItemName_.clear();
+            inventoryDirty = true;
+            ImGui::CloseCurrentPopup();
+        }
+        ImGui::SameLine();
+        if (ImGui::Button("Cancel", ImVec2(55, 0))) {
+            splitItemName_.clear();
+            ImGui::CloseCurrentPopup();
+        }
+        ImGui::EndPopup();
+    }
+
     // Draw held item at cursor
     renderHeldItem();
 }
@@ -2302,9 +2331,25 @@ void InventoryScreen::renderItemSlot(game::Inventory& inventory, const game::Ite
             }
         }
 
-        // Shift+right-click: open destroy confirmation for non-quest items
+        // Shift+right-click: split stack (if stackable >1) or destroy confirmation
         if (ImGui::IsItemHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Right) &&
-            !holdingItem && ImGui::GetIO().KeyShift && item.itemId != 0 && item.bindType != 4) {
+            !holdingItem && ImGui::GetIO().KeyShift && item.itemId != 0) {
+            if (item.stackCount > 1 && item.maxStack > 1) {
+                // Open split popup for stackable items
+                splitConfirmOpen_ = true;
+                splitItemName_ = item.name;
+                splitMax_ = static_cast<int>(item.stackCount);
+                splitCount_ = splitMax_ / 2;
+                if (splitCount_ < 1) splitCount_ = 1;
+                if (kind == SlotKind::BACKPACK && backpackIndex >= 0) {
+                    splitBag_ = 0xFF;
+                    splitSlot_ = static_cast<uint8_t>(23 + backpackIndex);
+                } else if (kind == SlotKind::BACKPACK && isBagSlot) {
+                    splitBag_ = static_cast<uint8_t>(19 + bagIndex);
+                    splitSlot_ = static_cast<uint8_t>(bagSlotIndex);
+                }
+            } else if (item.bindType != 4) {
+                // Destroy confirmation for non-quest, non-stackable items
                 destroyConfirmOpen_ = true;
                 destroyItemName_ = item.name;
                 destroyCount_ = static_cast<uint8_t>(std::clamp<uint32_t>(
@@ -2320,6 +2365,7 @@ void InventoryScreen::renderItemSlot(game::Inventory& inventory, const game::Ite
                     destroySlot_ = static_cast<uint8_t>(equipSlot);
                 }
             }
+        }
 
         // Right-click: bank deposit (if bank open), vendor sell (if vendor mode), or auto-equip/use
         // Note: InvisibleButton only tracks left-click by default, so use IsItemHovered+IsMouseClicked