Restore quick delete action in the sessions view

### Describe the feature or problem you'd like to solve

The sessions list used to support deleting a session directly from the list (a quick delete/keyboard action on the highlighted row). That option is gone, and there is now no good way to delete sessions.

### Proposed solution

• Re-add a delete action in the sessions view that operates on the highlighted session without opening it (e.g.  d  or  Del  key, with a confirmation prompt).
• Support deleting multiple sessions in one pass (multi-select, or stay in the list after each delete).
• Deleting from the list should not create a new session; the user should remain in the sessions view with the deleted entry removed.

### Example prompts or workflows

_No response_

### Additional context

The only remaining path is  /session delete , which has two significant problems:

1. It requires opening a session first. You must resume/enter a session before you can delete it, so cleaning up several stale sessions means repeatedly opening sessions you have no interest in.
2. It spawns a replacement session. After deleting, the CLI immediately creates a brand-new session. So deleting N sessions leaves you with N new empty sessions to clean up, which is extremely frustrating.

Start by tracing the sessions view and the existing `/session delete` command, especially how the highlighted row, keyboard actions, confirmation, and session creation are handled. Verify the current delete workflow first. Done means deleting one or more highlighted sessions from the list, removing them without opening them or creating replacement sessions, and keeping the user in the sessions view.

Written by the indexing model from the issue text.