TeamDelete fails after agents approve shutdown - 'active members' not cleared

Bug Description

After agents approve a shutdown_request, TeamDelete still fails with Cannot cleanup team with N active member(s). The agents have:

1. Responded with shutdown_response approve: true
2. System sent teammate_terminated message
3. But agents continue sending idle_notification after termination
4. TeamDelete still counts them as active members

Reproduction Steps

1. Create a team with TeamCreate
2. Spawn 2+ agents with Agent tool (team_name parameter)
3. Send shutdown_request to each agent
4. Wait for shutdown_response approve: true from each
5. Wait for teammate_terminated system message
6. Call TeamDelete
7. Expected: Team deleted successfully
8. Actual: Cannot cleanup team with N active member(s): agent1, agent2

Workaround

Force-removing team directories: rm -r ~/.claude/teams/{name} ~/.claude/tasks/{name}

Environment

• Claude Code version: 2.1.81
• OS: macOS Darwin 25.2.0 (Apple Silicon)
• Model: Claude Opus 4.6 (1M context)

Impact

In long sessions with multiple team cycles (20+ agent spawns across 6+ teams), every TeamDelete fails. This forces manual directory cleanup and prevents clean team lifecycle management.