Team in-process mode: process residue on disband + agents don't consume task_assignment

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Summary

The in-process backend for team mode has two related bugs:

1. Process residue: When a team is disbanded (TeamDelete), child agent processes (claude.exe + associated MCP servers like node.exe) are not killed. They remain as orphans consuming memory indefinitely.
2. Communication dead-loop: In-process agents spawn, report idle_notification, but never consume task_assignment messages from their inbox. They loop "available" without doing any work.

Reproduction

Environment: Windows 11 Pro (10.0.26200), Claude Code v2.1.150, no WSL.

1. Create a team with multiple agents using backendType: "in-process"
2. Assign tasks via inbox task_assignment messages
3. Observe: agents send idle_notification repeatedly but never execute tasks
4. Disband the team (TeamDelete)
5. Observe: claude.exe and node.exe (MCP) processes remain running

Evidence

Process residue

After disbanding 2 teams (test-team 3 agents, factor-mining-phase1 11 agents):

5 claude.exe processes left (oldest: 5 days)
9 node.exe MCP MySQL server processes left

Communication failure

test-team inbox analysis:

• team-lead asked researcher and git-checker to run git log --oneline -5
• Both agents only sent idle_notification (idleReason: "available")
• Both received shutdown_request (read: true) but never reported results
• Zero task output produced

factor-mining-phase1 (11 agents):

• 5 Phase 1 agents: only idle_notifications, zero task output
• 1 agent (phase2-minute-search): succeeded (only one using Explore type)
• Remaining agents: only idle_notifications + shutdown responses, no task output

Expected behavior

1. TeamDelete should terminate all child processes in the process tree
2. In-process agents should poll their inbox and execute task_assignment messages
3. Agents should report results back to team-lead inbox

Workaround

Use isolation: "worktree" instead of in-process — worktree agents have proper lifecycle management.

Environment

• OS: Windows 11 Pro (10.0.26200)
• Claude Code: v2.1.150
• Shell: PowerShell 5.1
• Terminal: VS Code + Windows Terminal
• No WSL, no MSYS2

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