Add Tier 7 commands: combat and trade

Combat Commands:
- /duel - Challenge target to a duel (CMSG_DUEL_PROPOSED 0x166)
- /trade - Open trade window with target (CMSG_INITIATE_TRADE 0x116)
- /startattack - Begin auto-attacking target
- /stopattack - Stop auto-attacking
- /stopcasting - Cancel current spell cast

New opcodes:
- CMSG_DUEL_PROPOSED (0x166) for initiating duels
- CMSG_INITIATE_TRADE (0x116) for starting trades

Packet builders:
- DuelProposedPacket - sends duel challenge to target GUID
- InitiateTradePacket - sends trade request to target GUID
- AttackSwingPacket, AttackStopPacket, CancelCastPacket reused from existing

Game handler methods:
- proposeDuel(targetGuid) - challenge target to duel
- initiateTrade(targetGuid) - open trade with target
- stopCasting() - cancel current spell cast (uses existing casting state)

All commands include validation for target selection and world state.
Removed duplicate packet class definitions from previous phases.

src/game/game_handler.cpp

@@ -2219,6 +2219,63 @@ void GameHandler::requestRaidInfo() {
     LOG_INFO("Requested raid info");
 }
 
+void GameHandler::proposeDuel(uint64_t targetGuid) {
+    if (state != WorldState::IN_WORLD || !socket) {
+        LOG_WARNING("Cannot propose duel: not in world or not connected");
+        return;
+    }
+
+    if (targetGuid == 0) {
+        addSystemChatMessage("You must target a player to challenge to a duel.");
+        return;
+    }
+
+    auto packet = DuelProposedPacket::build(targetGuid);
+    socket->send(packet);
+    addSystemChatMessage("You have challenged your target to a duel.");
+    LOG_INFO("Proposed duel to target: 0x", std::hex, targetGuid, std::dec);
+}
+
+void GameHandler::initiateTrade(uint64_t targetGuid) {
+    if (state != WorldState::IN_WORLD || !socket) {
+        LOG_WARNING("Cannot initiate trade: not in world or not connected");
+        return;
+    }
+
+    if (targetGuid == 0) {
+        addSystemChatMessage("You must target a player to trade with.");
+        return;
+    }
+
+    auto packet = InitiateTradePacket::build(targetGuid);
+    socket->send(packet);
+    addSystemChatMessage("Requesting trade with target.");
+    LOG_INFO("Initiated trade with target: 0x", std::hex, targetGuid, std::dec);
+}
+
+void GameHandler::stopCasting() {
+    if (state != WorldState::IN_WORLD || !socket) {
+        LOG_WARNING("Cannot stop casting: not in world or not connected");
+        return;
+    }
+
+    if (!casting) {
+        return; // Not casting anything
+    }
+
+    // Send cancel cast packet with current spell ID
+    auto packet = CancelCastPacket::build(currentCastSpellId);
+    socket->send(packet);
+
+    // Reset casting state
+    casting = false;
+    currentCastSpellId = 0;
+    castTimeRemaining = 0.0f;
+    castTimeTotal = 0.0f;
+
+    LOG_INFO("Cancelled spell cast");
+}
+
 void GameHandler::releaseSpirit() {
     if (!playerDead_) return;
     if (socket && state == WorldState::IN_WORLD) {

src/game/world_packets.cpp

@@ -1452,6 +1452,45 @@ network::Packet RequestRaidInfoPacket::build() {
     return packet;
 }
 
+// ============================================================
+// Combat and Trade
+// ============================================================
+
+network::Packet DuelProposedPacket::build(uint64_t targetGuid) {
+    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_DUEL_PROPOSED));
+    packet.writeUInt64(targetGuid);
+    LOG_DEBUG("Built CMSG_DUEL_PROPOSED for target: 0x", std::hex, targetGuid, std::dec);
+    return packet;
+}
+
+network::Packet InitiateTradePacket::build(uint64_t targetGuid) {
+    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_INITIATE_TRADE));
+    packet.writeUInt64(targetGuid);
+    LOG_DEBUG("Built CMSG_INITIATE_TRADE for target: 0x", std::hex, targetGuid, std::dec);
+    return packet;
+}
+
+network::Packet AttackSwingPacket::build(uint64_t targetGuid) {
+    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_ATTACKSWING));
+    packet.writeUInt64(targetGuid);
+    LOG_DEBUG("Built CMSG_ATTACKSWING for target: 0x", std::hex, targetGuid, std::dec);
+    return packet;
+}
+
+network::Packet AttackStopPacket::build() {
+    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_ATTACKSTOP));
+    LOG_DEBUG("Built CMSG_ATTACKSTOP");
+    return packet;
+}
+
+network::Packet CancelCastPacket::build(uint32_t spellId) {
+    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_CANCEL_CAST));
+    packet.writeUInt32(0); // cast count/sequence
+    packet.writeUInt32(spellId);
+    LOG_DEBUG("Built CMSG_CANCEL_CAST for spell: ", spellId);
+    return packet;
+}
+
 // ============================================================
 // Random Roll
 // ============================================================
@@ -1777,19 +1816,6 @@ bool MonsterMoveParser::parse(network::Packet& packet, MonsterMoveData& data) {
 // Phase 2: Combat Core
 // ============================================================
 
-network::Packet AttackSwingPacket::build(uint64_t targetGuid) {
-    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_ATTACKSWING));
-    packet.writeUInt64(targetGuid);
-    LOG_DEBUG("Built CMSG_ATTACKSWING: target=0x", std::hex, targetGuid, std::dec);
-    return packet;
-}
-
-network::Packet AttackStopPacket::build() {
-    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_ATTACKSTOP));
-    LOG_DEBUG("Built CMSG_ATTACKSTOP");
-    return packet;
-}
-
 bool AttackStartParser::parse(network::Packet& packet, AttackStartData& data) {
     if (packet.getSize() < 16) return false;
     data.attackerGuid = packet.readUInt64();
@@ -1971,13 +1997,6 @@ network::Packet CastSpellPacket::build(uint32_t spellId, uint64_t targetGuid, ui
     return packet;
 }
 
-network::Packet CancelCastPacket::build(uint32_t spellId) {
-    network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_CANCEL_CAST));
-    packet.writeUInt32(0); // sequence
-    packet.writeUInt32(spellId);
-    return packet;
-}
-
 network::Packet CancelAuraPacket::build(uint32_t spellId) {
     network::Packet packet(static_cast<uint16_t>(Opcode::CMSG_CANCEL_AURA));
     packet.writeUInt32(spellId);

src/ui/game_screen.cpp

@@ -1398,6 +1398,68 @@ void GameScreen::sendChatMessage(game::GameHandler& gameHandler) {
                 return;
             }
 
+            // Combat and Trade commands
+            if (cmdLower == "duel") {
+                if (gameHandler.hasTarget()) {
+                    gameHandler.proposeDuel(gameHandler.getTargetGuid());
+                } else if (spacePos != std::string::npos) {
+                    // Target player by name (would need name-to-GUID lookup)
+                    game::MessageChatData msg;
+                    msg.type = game::ChatType::SYSTEM;
+                    msg.language = game::ChatLanguage::UNIVERSAL;
+                    msg.message = "You must target a player to challenge to a duel.";
+                    gameHandler.addLocalChatMessage(msg);
+                } else {
+                    game::MessageChatData msg;
+                    msg.type = game::ChatType::SYSTEM;
+                    msg.language = game::ChatLanguage::UNIVERSAL;
+                    msg.message = "You must target a player to challenge to a duel.";
+                    gameHandler.addLocalChatMessage(msg);
+                }
+                chatInputBuffer[0] = '\0';
+                return;
+            }
+
+            if (cmdLower == "trade") {
+                if (gameHandler.hasTarget()) {
+                    gameHandler.initiateTrade(gameHandler.getTargetGuid());
+                } else {
+                    game::MessageChatData msg;
+                    msg.type = game::ChatType::SYSTEM;
+                    msg.language = game::ChatLanguage::UNIVERSAL;
+                    msg.message = "You must target a player to trade with.";
+                    gameHandler.addLocalChatMessage(msg);
+                }
+                chatInputBuffer[0] = '\0';
+                return;
+            }
+
+            if (cmdLower == "startattack") {
+                if (gameHandler.hasTarget()) {
+                    gameHandler.startAutoAttack(gameHandler.getTargetGuid());
+                } else {
+                    game::MessageChatData msg;
+                    msg.type = game::ChatType::SYSTEM;
+                    msg.language = game::ChatLanguage::UNIVERSAL;
+                    msg.message = "You have no target.";
+                    gameHandler.addLocalChatMessage(msg);
+                }
+                chatInputBuffer[0] = '\0';
+                return;
+            }
+
+            if (cmdLower == "stopattack") {
+                gameHandler.stopAutoAttack();
+                chatInputBuffer[0] = '\0';
+                return;
+            }
+
+            if (cmdLower == "stopcasting") {
+                gameHandler.stopCasting();
+                chatInputBuffer[0] = '\0';
+                return;
+            }
+
             // Chat channel slash commands
             bool isChannelCommand = false;
             if (cmdLower == "s" || cmdLower == "say") {