feat: add notifications for MacOS using Applescript (#160)

yolo'ed it with codex. Let me know if this looks good to you.

https://github.com/openai/codex/issues/148

tested with:
```
npm run build:dev
```

<img width="377" alt="Screenshot 2025-04-16 at 18 12 01"
src="https://github.com/user-attachments/assets/79aa799b-b0b9-479d-84f1-bfb83d34bfb9"
/>

codex-cli/tests/agent-cancel-early.test.ts

@@ -96,7 +96,7 @@ describe("cancel before first function_call", () => {
       onLoading: () => {},
       getCommandConfirmation: async () => ({ review: "yes" } as any),
       onLastResponseId: () => {},
-      config: { model: "any", instructions: "" },
+      config: { model: "any", instructions: "", notify: false },
     });
 
     // Start first run.