- Fix pre-existing ruff lint warnings (F401, F541, F841, E741)
- Exclude .md/.json/.yml from ruff format check
- Unblock SIGTERM/SIGINT via pthread_sigmask in early signal handler
- Do not restore SIG_DFL on unregister to prevent pending signal kills
- Register SIGTERM/SIGINT handlers in training loop, set stop flag on signal
- Check stop_requested at each epoch/batch boundary, break and call on_error to save checkpoint
- LocalStrategy parent forwards signal to child processes via terminate(), waits up to 600s for graceful exit
- TrainContext gains threading.Event-based stop_requested/request_stop
- Tests verify SIGTERM/SIGINT trigger checkpoint save with exit code 0, works on both CPU and GPU
ViperEkura