Argus is a free VS Code extension that puts all of it in one window. It uses the native Claude/Codex extensions (so a bit buggy, I'm hacking around their internals), and sorry about the shit onboarding, it's a preview.
T3 Code looks like a very good alternative if you'd rather have a standalone app; this one's for staying inside VS Code.
If folks like this I'll put some more effort getting it in good shape (this version was good enough for me rn lol)