## Why
Untouched threads have no rollout for `thread/resume` yet. Switching away from a blank startup or fresh session needs to preserve its live subscription, draft, and settings so it can be reopened.
## What changed
- Retain blank startup and fresh sessions for non-ephemeral connections to an external app server, and save their input state before navigating away.
- Restore the current thread name and apply background settings updates after restoring drafts, so saved model choices do not overwrite newer server settings.
## Testing
Extend the task-switching regression test to cover blank startup and fresh sessions, preserved drafts and model choices, updated thread names, and restoration without `thread/resume` or `thread/unsubscribe`. Verify that background model, permission, and approval-policy updates are used for the first submitted turn.
GitOrigin-RevId: 958b0cb48a5a873d8d8f5858ac334fecbfad60c7
Eric Traut
8f195c93d7