tbc: fix SMSG_CAST_RESULT — no castCount prefix in TBC 2.4.3

TBC 2.4.3 SMSG_CAST_RESULT sends spellId(u32) + result(u8) = 5 bytes.
WotLK 3.3.5a added a castCount(u8) prefix making it 6 bytes.  Without
this fix the WotLK parser was reading spellId[0] as castCount, then the
remaining 3 spellId bytes plus result byte as spellId (wrong), and then
whatever follows as result — producing incorrect failure messages and
potentially not clearing the cast bar on TBC.

Add TbcPacketParsers::parseCastResult override and a virtual base method,
then route SMSG_CAST_RESULT through virtual dispatch in the game handler.

include/game/packet_parsers.hpp

@@ -110,6 +110,19 @@ public:
         return CastFailedParser::parse(packet, data);
     }
 
+    /** Parse SMSG_CAST_RESULT header (spellId + result), expansion-aware.
+     *  WotLK: castCount(u8) + spellId(u32) + result(u8)
+     *  TBC/Classic: spellId(u32) + result(u8)  (no castCount prefix)
+     */
+    virtual bool parseCastResult(network::Packet& packet, uint32_t& spellId, uint8_t& result) {
+        // WotLK default: skip castCount, read spellId + result
+        if (packet.getSize() - packet.getReadPos() < 6) return false;
+        packet.readUInt8();  // castCount
+        spellId = packet.readUInt32();
+        result  = packet.readUInt8();
+        return true;
+    }
+
     /** Parse SMSG_AURA_UPDATE / SMSG_AURA_UPDATE_ALL */
     virtual bool parseAuraUpdate(network::Packet& packet, AuraUpdateData& data, bool isAll = false) {
         return AuraUpdateParser::parse(packet, data, isAll);
@@ -307,6 +320,8 @@ public:
     bool parseMonsterMove(network::Packet& packet, MonsterMoveData& data) override;
     // TBC 2.4.3 SMSG_GOSSIP_MESSAGE quests lack questFlags(u32)+isRepeatable(u8) (WotLK added them)
     bool parseGossipMessage(network::Packet& packet, GossipMessageData& data) override;
+    // TBC 2.4.3 SMSG_CAST_RESULT: spellId(u32) + result(u8) — WotLK added castCount(u8) prefix
+    bool parseCastResult(network::Packet& packet, uint32_t& spellId, uint8_t& result) override;
     // TBC 2.4.3 SMSG_MAIL_LIST_RESULT: uint8 count (not uint32+uint8), no body field,
     // attachment uses uint64 itemGuid (not uint32), enchants are 7×u32 id-only (not 7×{id+dur+charges})
     bool parseMailList(network::Packet& packet, std::vector<MailMessage>& inbox) override;

src/game/game_handler.cpp

@@ -1742,28 +1742,28 @@ void GameHandler::handlePacket(network::Packet& packet) {
         }
 
         // ---- Cast result (WotLK extended cast failed) ----
-        case Opcode::SMSG_CAST_RESULT:
+        case Opcode::SMSG_CAST_RESULT: {
-            // WotLK: uint8 castCount + uint32 spellId + uint8 result [+ optional extra]
+            // WotLK: castCount(u8) + spellId(u32) + result(u8)
+            // TBC/Classic: spellId(u32) + result(u8)  (no castCount prefix)
             // If result == 0, the spell successfully began; otherwise treat like SMSG_CAST_FAILED.
-            if (packet.getSize() - packet.getReadPos() >= 6) {
+            uint32_t castResultSpellId = 0;
-                /*uint8_t castCount =*/ packet.readUInt8();
+            uint8_t  castResult        = 0;
-                /*uint32_t spellId  =*/ packet.readUInt32();
+            if (packetParsers_->parseCastResult(packet, castResultSpellId, castResult)) {
-                uint8_t  result    = packet.readUInt8();
+                if (castResult != 0) {
-                if (result != 0) {
-                    // Failure — clear cast bar and show message
                     casting = false;
                     currentCastSpellId = 0;
                     castTimeRemaining  = 0.0f;
-                    const char* reason = getSpellCastResultString(result, -1);
+                    const char* reason = getSpellCastResultString(castResult, -1);
                     MessageChatData msg;
                     msg.type     = ChatType::SYSTEM;
                     msg.language = ChatLanguage::UNIVERSAL;
                     msg.message  = reason ? reason
-                                          : ("Spell cast failed (error " + std::to_string(result) + ")");
+                                          : ("Spell cast failed (error " + std::to_string(castResult) + ")");
                     addLocalChatMessage(msg);
                 }
             }
             break;
+        }
 
         // ---- Spell failed on another unit ----
         case Opcode::SMSG_SPELL_FAILED_OTHER:

src/game/packet_parsers_tbc.cpp

@@ -977,6 +977,21 @@ bool TbcPacketParsers::parseMailList(network::Packet& packet, std::vector<MailMe
     return !inbox.empty();
 }
 
+// ============================================================================
+// TbcPacketParsers::parseCastResult — TBC 2.4.3 SMSG_CAST_RESULT
+//
+// TBC format: spellId(u32) + result(u8) = 5 bytes
+// WotLK adds a castCount(u8) prefix making it 6 bytes.
+// Without this override, WotLK parser reads spellId[0] as castCount,
+// then the remaining 4 bytes as spellId (off by one), producing wrong result.
+// ============================================================================
+bool TbcPacketParsers::parseCastResult(network::Packet& packet, uint32_t& spellId, uint8_t& result) {
+    if (packet.getSize() - packet.getReadPos() < 5) return false;
+    spellId = packet.readUInt32();   // No castCount prefix in TBC
+    result  = packet.readUInt8();
+    return true;
+}
+
 // ============================================================================
 // TbcPacketParsers::parseAttackerStateUpdate — TBC 2.4.3 SMSG_ATTACKERSTATEUPDATE
 //