feat: add plugin context, lifecycle, and schema validation

- Implemented PluginContextSchema, PluginLifecycleSchema, and PluginSchema using Zod for runtime validation.
- Added comprehensive unit tests for plugin context and lifecycle hooks.
- Created service registry schemas and tests for service metadata, configuration, and factory registration.
- Developed startup orchestrator schemas and tests for plugin startup options, health status, and orchestration results.

Author: hotlong

packages/spec/src/index.ts

@@ -47,6 +47,7 @@ export * as Data from './data';
 export * as Security from './security';
 export * as UI from './ui';
 export * as System from './system';
+export * as Kernel from './kernel';
 export * as QA from './qa';
 export * as Identity from './identity';
 export * as Hub from './hub';