refactor(tools): remove native ast-grep tool

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/plugin/tool-registry.test.ts

@@ -53,7 +53,6 @@ const toolFactories: NonNullable<Parameters<typeof createToolRegistry>[0]["toolF
   createSkillTool: mock(() => fakeTool),
   createGrepTools: mock(() => ({})),
   createGlobTools: mock(() => ({})),
-  createAstGrepTools: mock(() => ({})),
   createSessionManagerTools: mock(() => ({})),
   createDelegateTask: mock((options: { onSyncSessionCreated?: typeof syncSessionCreatedCallbacks[number] }) => {
     syncSessionCreatedCallbacks.push(options.onSyncSessionCreated)