refactor(game): extract EntityController from GameHandler (step 1.3)

Moves entity lifecycle, name/creature/game-object caches, transport GUID
tracking, and the entire update-object pipeline out of GameHandler into a
new EntityController class (friend-class pattern, same as CombatHandler
et al.).

What moved:
- applyUpdateObjectBlock() — 1,520-line core of all entity creation,
  field updates, and movement application
- processOutOfRangeObjects() / finalizeUpdateObjectBatch()
- handleUpdateObject() / handleCompressedUpdateObject() / handleDestroyObject()
- handleNameQueryResponse() / handleCreatureQueryResponse()
- handleGameObjectQueryResponse() / handleGameObjectPageText()
- handlePageTextQueryResponse()
- enqueueUpdateObjectWork() / processPendingUpdateObjectWork()
- playerNameCache, playerClassRaceCache_, pendingNameQueries
- creatureInfoCache, pendingCreatureQueries
- gameObjectInfoCache_, pendingGameObjectQueries_
- transportGuids_, serverUpdatedTransportGuids_
- EntityManager (accessed by other handlers via getEntityManager())

8 opcodes re-registered by EntityController::registerOpcodes():
  SMSG_UPDATE_OBJECT, SMSG_COMPRESSED_UPDATE_OBJECT, SMSG_DESTROY_OBJECT,
  SMSG_NAME_QUERY_RESPONSE, SMSG_CREATURE_QUERY_RESPONSE,
  SMSG_GAMEOBJECT_QUERY_RESPONSE, SMSG_GAMEOBJECT_PAGETEXT,
  SMSG_PAGE_TEXT_QUERY_RESPONSE

Other handler files (combat, movement, social, spell, inventory, quest,
chat) updated to access EntityManager via getEntityManager() and the
name cache via getPlayerNameCache() — no logic changes.

Also included:
- .clang-tidy: add modernize-use-nodiscard,
  modernize-use-designated-initializers; set -std=c++20 in ExtraArgs
- test.sh: prepend clang's own resource include dir before GCC's to
  silence xmmintrin.h / ia32intrin.h conflicts during clang-tidy runs

Line counts:
  entity_controller.hpp  147 lines  (new)
  entity_controller.cpp  2172 lines (new)
  game_handler.cpp       8095 lines (was 10143, −2048)

Build: 0 errors, 0 warnings.

src/game/chat_handler.cpp

@@ -138,8 +138,8 @@ void ChatHandler::sendChatMessage(ChatType type, const std::string& message, con
     echo.language = language;
     echo.message = message;
 
-    auto nameIt = owner_.playerNameCache.find(owner_.playerGuid);
-    if (nameIt != owner_.playerNameCache.end()) {
+    auto nameIt = owner_.getPlayerNameCache().find(owner_.playerGuid);
+    if (nameIt != owner_.getPlayerNameCache().end()) {
         echo.senderName = nameIt->second;
     }
 
@@ -179,11 +179,11 @@ void ChatHandler::handleMessageChat(network::Packet& packet) {
 
     // Resolve sender name from entity/cache if not already set by parser
     if (data.senderName.empty() && data.senderGuid != 0) {
-        auto nameIt = owner_.playerNameCache.find(data.senderGuid);
-        if (nameIt != owner_.playerNameCache.end()) {
+        auto nameIt = owner_.getPlayerNameCache().find(data.senderGuid);
+        if (nameIt != owner_.getPlayerNameCache().end()) {
             data.senderName = nameIt->second;
         } else {
-            auto entity = owner_.entityManager.getEntity(data.senderGuid);
+            auto entity = owner_.getEntityManager().getEntity(data.senderGuid);
             if (entity) {
                 if (entity->getType() == ObjectType::PLAYER) {
                     auto player = std::dynamic_pointer_cast<Player>(entity);
@@ -356,11 +356,11 @@ void ChatHandler::handleTextEmote(network::Packet& packet) {
     }
 
     std::string senderName;
-    auto nameIt = owner_.playerNameCache.find(data.senderGuid);
-    if (nameIt != owner_.playerNameCache.end()) {
+    auto nameIt = owner_.getPlayerNameCache().find(data.senderGuid);
+    if (nameIt != owner_.getPlayerNameCache().end()) {
         senderName = nameIt->second;
     } else {
-        auto entity = owner_.entityManager.getEntity(data.senderGuid);
+        auto entity = owner_.getEntityManager().getEntity(data.senderGuid);
         if (entity) {
             auto unit = std::dynamic_pointer_cast<Unit>(entity);
             if (unit) senderName = unit->getName();
@@ -685,7 +685,7 @@ void ChatHandler::handleChannelList(network::Packet& packet) {
         uint64_t memberGuid = packet.readUInt64();
         uint8_t memberFlags = packet.readUInt8();
         std::string name;
-        auto entity = owner_.entityManager.getEntity(memberGuid);
+        auto entity = owner_.getEntityManager().getEntity(memberGuid);
         if (entity) {
             auto player = std::dynamic_pointer_cast<Player>(entity);
             if (player && !player->getName().empty()) name = player->getName();