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/editor_app.hpp

@@ -54,6 +54,7 @@ public:
     QuestEditor& getQuestEditor() { return questEditor_; }
     AssetBrowser& getAssetBrowser() { return assetBrowser_; }
     EditorViewport& getViewport() { return viewport_; }
+    void setMapName(const std::string& name) { loadedMap_ = name; }
     rendering::TerrainRenderer* getTerrainRenderer();
     rendering::M2Renderer* getM2Renderer() { return viewport_.getM2Renderer(); }
     pipeline::AssetManager* getAssetManager() { return assetManager_.get(); }