Notification sound and sidebar pulse when a thread needs input or finishes

[CDVolvik]

I built this for myself as a local hack and it changed how I use T3 Code, so I want to check whether an in-app version is welcome before anyone writes code.

The problem: I run several threads and I miss when one finishes or stops for approval. Nothing makes a sound, and the Input badge in the thread list does not move. I would tab away and come back minutes later to a thread that had been waiting the whole time.

What I did locally: Claude Code Stop and Notification hooks that play a sound, flash the Windows taskbar, and pop a toast. The difference is bigger than I expected. Before, I did not notice when a terminal was done. Now I can keep track of several at once without watching them.

Why it belongs in the app: my version only covers Claude Code on Windows. It also cannot touch the one signal I actually want, which is the Input badge in the left thread list pulsing. A hook is an external process, so the sidebar is out of reach. In-app it would work for every provider and every platform.

What I would propose, as separate small PRs rather than one big one:

1. sound on turn complete, approval, and question, with a focus rule
2. settings section to toggle each event
3. custom sound file, plus a few bundled defaults
4. pulse on the Input badge in the thread list

I read CONTRIBUTING and I know you are not taking contributions right now. I also saw #2373, #4003, #976, #1657 and #1780 go nowhere. I am not trying to be the sixth. If this is already on your roadmap, or you do not want it, say so and I will keep my local hack. If a scoped version would get reviewed, I will build only number 1 and keep it small.