feat(kit): add core skill plugin capabilities

packages/kit/package.json

@@ -77,6 +77,7 @@
   },
   "dependencies": {
     "idb": "^8.0.3",
+    "vite": "6",
     "yaml": "^2.8.3"
   }
 }

packages/kit/src/message/plugins/index.ts

@@ -1,4 +1,6 @@
 export { lengthPlugin } from './lengthPlugin'
+export { getSkillRequestContext, mergeSystemInstructions, skillPlugin } from './skillPlugin'
+export type { InjectSkillInstructions, SkillPluginOptions, SkillRequestContext, SkillSelection } from './skillPlugin'
 export { thinkingPlugin } from './thinkingPlugin'
 export { toolPlugin } from './toolPlugin'
 export type { RuntimeTool, ToolCallContext, ToolProvider, ToolProviderItem, ToolSource } from './toolPlugin'