feat(editor): zone manifest for client loading, export workflow complete

- Zone manifest (zone.json): generated on export with map name, map ID,
  tile list, biome, creature flag, and file paths. This is what the
  wowee client will read to discover and load custom zones.
- Export workflow now produces a complete loadable zone package:
  zone.json + MapName.wdt + MapName_X_Y.adt + creatures.json
- ZoneManifest class with save/load (JSON format)
- Custom map IDs start at 9000+ to avoid conflicting with retail maps
- New Terrain dialog shows helper text for map name format

tools/editor/zone_manifest.cpp

@@ -0,0 +1,77 @@
+#include "zone_manifest.hpp"
+#include "core/logger.hpp"
+#include <fstream>
+#include <filesystem>
+
+namespace wowee {
+namespace editor {
+
+bool ZoneManifest::save(const std::string& path) const {
+    auto dir = std::filesystem::path(path).parent_path();
+    if (!dir.empty()) std::filesystem::create_directories(dir);
+
+    std::ofstream f(path);
+    if (!f) { LOG_ERROR("Failed to write zone manifest: ", path); return false; }
+
+    f << "{\n";
+    f << "  \"mapName\": \"" << mapName << "\",\n";
+    f << "  \"displayName\": \"" << displayName << "\",\n";
+    f << "  \"mapId\": " << mapId << ",\n";
+    f << "  \"biome\": \"" << biome << "\",\n";
+    f << "  \"baseHeight\": " << baseHeight << ",\n";
+    f << "  \"hasCreatures\": " << (hasCreatures ? "true" : "false") << ",\n";
+    f << "  \"description\": \"" << description << "\",\n";
+    f << "  \"tiles\": [";
+    for (size_t i = 0; i < tiles.size(); i++) {
+        f << "[" << tiles[i].first << "," << tiles[i].second << "]";
+        if (i + 1 < tiles.size()) f << ",";
+    }
+    f << "],\n";
+    f << "  \"files\": {\n";
+    f << "    \"wdt\": \"" << mapName << ".wdt\",\n";
+    for (size_t i = 0; i < tiles.size(); i++) {
+        f << "    \"adt_" << tiles[i].first << "_" << tiles[i].second << "\": \""
+          << mapName << "_" << tiles[i].first << "_" << tiles[i].second << ".adt\"";
+        if (i + 1 < tiles.size() || hasCreatures) f << ",";
+        f << "\n";
+    }
+    if (hasCreatures)
+        f << "    \"creatures\": \"creatures.json\"\n";
+    f << "  }\n";
+    f << "}\n";
+
+    LOG_INFO("Zone manifest saved: ", path);
+    return true;
+}
+
+bool ZoneManifest::load(const std::string& path) {
+    std::ifstream f(path);
+    if (!f) return false;
+    std::string content((std::istreambuf_iterator<char>(f)),
+                         std::istreambuf_iterator<char>());
+
+    auto findStr = [&](const std::string& key) -> std::string {
+        auto pos = content.find("\"" + key + "\"");
+        if (pos == std::string::npos) return "";
+        pos = content.find('"', content.find(':', pos) + 1);
+        if (pos == std::string::npos) return "";
+        auto end = content.find('"', pos + 1);
+        return content.substr(pos + 1, end - pos - 1);
+    };
+
+    mapName = findStr("mapName");
+    displayName = findStr("displayName");
+    biome = findStr("biome");
+    description = findStr("description");
+
+    auto numPos = content.find("\"mapId\"");
+    if (numPos != std::string::npos) {
+        numPos = content.find(':', numPos);
+        mapId = static_cast<uint32_t>(std::stoi(content.substr(numPos + 1)));
+    }
+
+    return !mapName.empty();
+}
+
+} // namespace editor
+} // namespace wowee