fix: skip force-kill logging when no processes remain - #616

Summary

• avoid logging a force-kill event when no processes remain killable
• cover processes that exit after the initial termination signal

Problem

When killTimeout is enabled, a process may exit normally after receiving the initial termination signal. The timeout callback currently treats the resulting empty command array as truthy and logs Sending SIGKILL to 0 processes.., even though no force kill occurs.

Fix

Only log and send SIGKILL when the timeout callback finds at least one process that is still killable.

Testing

• pnpm vitest run --project unit lib/flow-control/kill-others.spec.ts
• CI=1 pnpm test
• pnpm exec vitest --coverage
• pnpm typecheck
• pnpm lint
• pnpm format
• pnpm build
• pnpm test:smoke