[FEATURE] Desktop app: merge Chat, Cowork and Code into one interface

The desktop app splits work across Chat, Cowork and Code, and Code has a different interface from the other two. So I have to decide which mode a task belongs in before I start, and moving between them breaks my flow. Codex's desktop app uses one interface for everything. Please consider one unified workspace where a conversation can use chat, file work or coding tools as needed, without switching tabs or starting a new session.

Platform: Linux