## Summary
- When a child process crashes and a retry (`RETRY_IMMEDIATELY`) is
attempted on the same `TaskRunProcess`, `execute()` hangs forever
because the IPC send is silently skipped and the attempt promise can
never resolve
- This caused runner pods to stay up indefinitely with no heartbeats or
polls
- Fix: reject the attempt promise immediately when the child is not
connected, so the controller can proceed to warm start or exit
## Test plan
- [x] Added `taskRunProcess.test.ts` — verifies `execute()` rejects
promptly instead of hanging when the child process is dead
- [x] Deploy and verify no more stuck runner pods accumulate over time
nicktrn
279102c17c