feat: scaffold mvp shell and content runtime

js/content/registry/city-registry.js

@@ -0,0 +1,30 @@
+export function createCityRegistry(cities) {
+  const cityMap = new Map(
+    [...cities]
+      .sort((left, right) => left.sortOrder - right.sortOrder)
+      .map((city) => [city.id, city]),
+  )
+
+  return {
+    getAllCities() {
+      return [...cityMap.values()]
+    },
+    getCity(cityId) {
+      return cityMap.get(cityId) ?? null
+    },
+    listCitiesByContinent(continentId) {
+      return [...cityMap.values()].filter((city) => city.continentId === continentId)
+    },
+    getLevelPreset(cityId, levelId) {
+      const city = cityMap.get(cityId)
+
+      if (!city) {
+        return null
+      }
+
+      return city.levelPresets.find((preset) => preset.id === levelId) ?? null
+    },
+  }
+}
+
+export default createCityRegistry