feat(editor): Export Content Pack button in File menu

- File > Export Content Pack (.wcp) saves zone + packs into WCP archive
- Auto-saves zone first, then bundles into the novel WCP format
- WCP is a custom format unique to wowee (not MPQ, not CASC)
- Output: output/MapName.wcp ready for distribution
- Toast notification on success/failure

tools/editor/editor_app.hpp

@@ -36,6 +36,7 @@ public:
     void saveWDT(const std::string& path);
     void exportZone(const std::string& outputDir);
     void quickSave();
+    void exportContentPack(const std::string& destPath);
 
     void requestQuit();
     void resetCamera();