Add Kernel export and move tests to kernel directory

Exported the Kernel module in index.ts and relocated manifest and plugin test files from the system directory to the kernel directory for better organization.

Author: hotlong

packages/spec/src/index.ts

@@ -46,6 +46,7 @@ export * as Driver from './driver';
 export * as Permission from './permission';
 export * as UI from './ui';
 export * as System from './system';
+export * as Kernel from './kernel';
 export * as AI from './ai';
 export * as API from './api';
 export * as Automation from './automation';