1. Export route: stop_training() only signals the subprocess — wait up to
30s for it to actually exit before loading the export checkpoint, avoiding
a GPU memory race.
2. Training reset: clear _should_stop so /api/train/status returns phase=idle
instead of staying stuck on phase=stopped after a user-triggered stop.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>