fix(ecs): resolve ESM require is not defined error (#402)

- Add RuntimeConfig module as standalone runtime environment storage
- Core.runtimeEnvironment and Scene.runtimeEnvironment now read from RuntimeConfig
- Remove require() call in Scene.ts to fix Node.js ESM compatibility

Fixes ReferenceError: require is not defined when using scene.isServer in ESM environment

packages/framework/core/src/index.ts

@@ -5,6 +5,7 @@
 
 // 核心模块
 export { Core } from './Core';
+export { RuntimeConfig } from './RuntimeConfig';
 export { ServiceContainer, ServiceLifetime } from './Core/ServiceContainer';
 export type { IService, ServiceType, ServiceIdentifier } from './Core/ServiceContainer';