fix(invoke): resolve signalDone grace period race condition

[jlia0]

Description

Fix a race condition in runCommandStreaming where the signalDone grace period handler kills the subprocess with SIGTERM, which triggers the close event with exit code 143 before the delayed settle(0) can run. This causes a spurious rejection and the agent returns a generic error message instead of the successfully streamed result.

Changes

• Call settle(0) before child.kill('SIGTERM') so the promise resolves successfully and the subsequent close event (code 143) is a no-op
• Remove the unnecessary nested setTimeout(() => settle(0), 2000) since settling now happens synchronously before the kill

Testing

• Reviewed the control flow to confirm settle guards on settled flag, so the close event after kill is safely ignored

Checklist

• PR title follows conventional commit format (type(scope): description)
• I have tested these changes locally
• My changes don't introduce new warnings or errors
• I have updated documentation if needed