feat(editor): stamp persistence, WCP file preview, enriched stats

- Terrain stamps save/load to JSON: reuse terrain features across zones
  and sessions. Save/Load buttons in Sculpt > Stamp/Clone panel
- WCP Inspect now shows full file breakdown: terrain/model/building/
  texture/data counts with total size. Powered by readInfo file list
  parsing with auto-categorization by extension
- stats.json now includes chunk count, triangle count, tile count, and
  editor version alongside existing object/NPC/quest/texture counts
- Fix unprotected std::stoi in custom zone WOT filename parser

tools/editor/editor_app.cpp

@@ -1040,6 +1040,13 @@ void EditorApp::exportZone(const std::string& outputDir) {
         sj["textures"] = usedTextures.size();
         sj["openFormatScore"] = score;
         sj["formats"] = validation.summary();
+        sj["tiles"] = static_cast<int>(manifest.tiles.size());
+        auto* tr = viewport_.getTerrainRenderer();
+        if (tr) {
+            sj["chunks"] = tr->getChunkCount();
+            sj["triangles"] = tr->getTriangleCount();
+        }
+        sj["editorVersion"] = "1.0.0";
         std::ofstream stats(base + "/stats.json");
         if (stats) stats << sj.dump(2) << "\n";
     }