nav: 统一 NavNode schema + runtime/roadmap 分离 + 城市补父级

- navigation/nav-schema.js: 统一 NavNode schema 定义
- navigation/runtime-nav.js: MVP runtime（仅 6 城市 active）
- navigation/future-catalog.js: 路线图数据（不进 runtime）
- 旧索引文件标注 @deprecated，重定向到新路径
- 6 城市补 countryId/regionId
- game-design 明确 MVP vs V1.1+ 导航边界

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

js/content/cities/index.js

@@ -0,0 +1,10 @@
+import bangkok from './bangkok.js'
+import beijing from './beijing.js'
+import istanbul from './istanbul.js'
+import seoul from './seoul.js'
+import singapore from './singapore.js'
+import tokyo from './tokyo.js'
+
+export const cities = [beijing, tokyo, bangkok, seoul, singapore, istanbul]
+
+export default cities