[Bug] custom-tools/handler.ts double-kill timer leak

[akramcodez]

Description

After child.kill('SIGTERM'), an unref'd setTimeout(... 1000) schedules child.kill('SIGKILL'). If the child exited cleanly within 1s, the timer still fires and calls kill on a dead process (the !child.killed guard doesn't reliably catch it).

Environment

• OS: Any
• Node version: v22.20.0
• Nanocoder version: 1.30.0
• Provider: N/A
• Model: N/A

Steps to Reproduce

1. Run a custom tool that terminates immediately upon receiving SIGTERM.
2. Wait 1 second and monitor process logs.

Expected Behavior

The SIGKILL timer should be cleared when the process exits.

Actual Behavior

The timer fires, attempting to kill a dead process, potentially causing an unhandled error or noisy warning.

Additional Context

• I have searched existing issues to ensure this is not a duplicate
• I can reproduce this issue consistently
• This issue occurs with the latest version of nanocoder