MCP server processes not killed on CLI exit

[dxxhust]

Describe the bug

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Affected version

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Steps to reproduce the behavior

Body: After exiting copilot, ssh-mcp (and other MCP) child processes remain alive in Activity Monitor. Each
consumes ~tens of MB. Expected behavior: CLI should send SIGTERM to all spawned MCP child processes on exit.
Steps to reproduce: 1. Start copilot with SSH MCP servers configured. 2. Exit with Ctrl+D or /exit. 3. Run
pgrep -la mcp — processes still alive.

Expected behavior

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Additional context

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