fix(editor): ID counter resets, quest panel guard, zone rename, load paths

Bug fixes:
- ObjectPlacer::clearAll() now resets uniqueIdCounter_ to 1
- NpcSpawner::clearAll() added with idCounter_ reset (was manual clear)
- clearAllObjects() uses NpcSpawner::clearAll() instead of manual clear
- Quest panel has terrain-loaded guard (prevents crash before loading)

Features:
- Zone rename: editable map name field in Info panel (press Enter)
- Load objects/creatures/quests from both output/ and custom_zones/
  directories (WOT zones from custom_zones now get their NPCs loaded)

tools/editor/npc_spawner.hpp

@@ -73,6 +73,7 @@ public:
     const std::vector<CreatureSpawn>& getSpawns() const { return spawns_; }
     std::vector<CreatureSpawn>& getSpawns() { return spawns_; }
     size_t spawnCount() const { return spawns_.size(); }
+    void clearAll() { spawns_.clear(); selectedIdx_ = -1; idCounter_ = 1; }
 
     // Serialize to/from JSON
     bool saveToFile(const std::string& path) const;