[Feature Request] Add setting for changing launch Mode for all chats - Interactive vs. Autopilot

### Feature summary

Add new settings under Sessions

### What problem are you trying to solve?

* I find myself starting new chat sessions, and the mode is always default to "Interactive".
* I'd love for this to be a setting so I can configure it to be "Autopilot" by default for all new chats.

### Proposed solution

* A new setting under Sessions (similar to default Model setting) could be a god-send.

### Workflow impact

Make it one less quick when starting new chats.

### Installation context

_No response_

### Additional context

_No response_

Start in the Sessions settings and compare the proposed option with the existing default Model setting. Trace how a new chat chooses Interactive versus Autopilot, then verify that the selected setting controls the mode for every newly created chat.

Written by the indexing model from the issue text.