[FEATURE] Agent view: Ctrl+X on a group header deletes the whole group — add confirmation and undo

Environment

• Claude Code 2.1.260 (macOS, Darwin 25.5)
• claude agents (agent view), fleetViewGroupMode: state

Problem

In agent view, Ctrl+X on a group header deletes every session in that group. The docs say this happens "after confirmation", but the confirmation is the same gesture as a single-row delete (press Ctrl+X again within two seconds). Muscle memory from deleting individual rows makes it trivial to wipe the whole Working group by accident — the cursor only has to be one row above the first session.

Losing the rows is recoverable in principle (/resume in the dispatch input lists deleted sessions), but:

• there is no undo for the gesture itself,
• a group delete on Working targets live sessions mid-turn, which is a very different action from dismissing a Completed row,
• and it is not obvious from the UI which sessions were affected or how to bring them back.

Expected

One or more of:

1. A distinct, explicit confirmation for group deletes — e.g. type y/Enter on a prompt that lists the N sessions that will be deleted — instead of the 2-second double-press.
2. Refuse (or require an extra step) when the group contains sessions that are currently working; or stop them first and only delete on a second, separate action.
3. A short-lived undo ("Deleted 4 sessions — press U to restore") that re-lists the rows.
4. A hint after deletion pointing at /resume for recovery.