game: fix NPCs not spawning on reconnect to same map

On disconnect/reconnect to the same map, entityManager was not cleared
and creatureInstances_ still held old entries from the previous session.
When the server re-sent CREATE_OBJECT for the same GUIDs, the spawn
callback's early-return guard (creatureInstances_.count(guid)) silently
dropped every NPC re-spawn, leaving the world empty.

Fixes:
- disconnect() now calls entityManager.clear() to purge stale entities
- WorldEntryCallback gains a bool isInitialEntry parameter (true on first
  login or reconnect, false on in-world teleport/flight landing)
- Same-map optimization path skipped when isInitialEntry=true, so
  loadOnlineWorldTerrain runs its full cleanup and properly despawns old
  creature/player instances before the server refreshes them

include/game/game_handler.hpp

@@ -666,8 +666,8 @@ public:
     uint32_t getSkillCategory(uint32_t skillId) const;
 
     // World entry callback (online mode - triggered when entering world)
-    // Parameters: mapId, x, y, z (canonical WoW coordinates)
-    using WorldEntryCallback = std::function<void(uint32_t mapId, float x, float y, float z)>;
+    // Parameters: mapId, x, y, z (canonical WoW coords), isInitialEntry=true on first login or reconnect
+    using WorldEntryCallback = std::function<void(uint32_t mapId, float x, float y, float z, bool isInitialEntry)>;
     void setWorldEntryCallback(WorldEntryCallback cb) { worldEntryCallback_ = std::move(cb); }
 
     // Unstuck callback (resets player Z to floor height)

src/core/application.cpp

@@ -1692,13 +1692,16 @@ void Application::setupUICallbacks() {
     });
 
     // World entry callback (online mode) - load terrain when entering world
-    gameHandler->setWorldEntryCallback([this](uint32_t mapId, float x, float y, float z) {
-        LOG_INFO("Online world entry: mapId=", mapId, " pos=(", x, ", ", y, ", ", z, ")");
+    gameHandler->setWorldEntryCallback([this](uint32_t mapId, float x, float y, float z, bool isInitialEntry) {
+        LOG_INFO("Online world entry: mapId=", mapId, " pos=(", x, ", ", y, ", ", z, ")"
+                 " initial=", isInitialEntry);
 
         // Same-map teleport (taxi landing, GM teleport on same continent):
         // just update position, let terrain streamer handle tile loading incrementally.
         // A full reload is only needed on first entry or map change.
-        if (mapId == loadedMapId_ && renderer && renderer->getTerrainManager()) {
+        // Exception: on reconnect to the same map (isInitialEntry=true), all online entities
+        // are stale and must be cleared so the server's fresh CREATE_OBJECTs re-spawn them.
+        if (mapId == loadedMapId_ && renderer && renderer->getTerrainManager() && !isInitialEntry) {
             LOG_INFO("Same-map teleport (map ", mapId, "), skipping full world reload");
             glm::vec3 canonical = core::coords::serverToCanonical(glm::vec3(x, y, z));
             glm::vec3 renderPos = core::coords::canonicalToRender(canonical);

src/game/game_handler.cpp

@@ -499,6 +499,8 @@ void GameHandler::disconnect() {
     wardenModuleSize_ = 0;
     wardenModuleData_.clear();
     wardenLoadedModule_.reset();
+    // Clear entity state so reconnect sees fresh CREATE_OBJECT for all visible objects.
+    entityManager.clear();
     setState(WorldState::DISCONNECTED);
     LOG_INFO("Disconnected from world server");
 }
@@ -6074,7 +6076,7 @@ void GameHandler::handleLoginVerifyWorld(network::Packet& packet) {
 
     // Notify application to load terrain for this map/position (online mode)
     if (worldEntryCallback_) {
-        worldEntryCallback_(data.mapId, data.x, data.y, data.z);
+        worldEntryCallback_(data.mapId, data.x, data.y, data.z, initialWorldEntry);
     }
 
     // Auto-join default chat channels
@@ -15582,7 +15584,7 @@ void GameHandler::handleTeleportAck(network::Packet& packet) {
     // Notify application of teleport — the callback decides whether to do
     // a full world reload (map change) or just update position (same map).
     if (worldEntryCallback_) {
-        worldEntryCallback_(currentMapId_, serverX, serverY, serverZ);
+        worldEntryCallback_(currentMapId_, serverX, serverY, serverZ, false);
     }
 }
 
@@ -15689,7 +15691,7 @@ void GameHandler::handleNewWorld(network::Packet& packet) {
 
     // Reload terrain at new position
     if (worldEntryCallback_) {
-        worldEntryCallback_(mapId, serverX, serverY, serverZ);
+        worldEntryCallback_(mapId, serverX, serverY, serverZ, false);
     }
 }